Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks all for your input! I've updated FLIP-57 accordingly. To summarize the changes: - introduced new concept of "Temporary system functions", which has no namespace and override built-in functions - repositioned "temporary functions" to be those with namespaces and override catalog functions - updated FunctionCatalog APIs - redefined the ambiguous function resolution order to be: 1. temporary system functions 2. builtin functions 3. temporary functions, of the current catalog/db 4. catalog functions, in the current catalog/db Since we've reached consensus on several most critical pieces of the FLIP, I've started a separate voting thread on it. Cheers, Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
"SYSTEM" sounds good to me too. Best, Jark On Mon, 23 Sep 2019 at 19:04, Fabian Hueske wrote: > +1 for CREATE TEMPORARY SYSTEM FUNCTION xxx > > Cheers, Fabian > > Am Sa., 21. Sept. 2019 um 06:58 Uhr schrieb Bowen Li >: > > > "SYSTEM" sounds good to me. FYI, this FLIP only impacts low level of the > > SQL function stack and won't actually involve any DDL, thus I will just > > document the decision and we should keep it in mind when it's time to > > implement the DDLs. > > > > I'm in the process of updating the FLIP to reflect changes required for > > option #2, will send a new version for review soon. > > > > > > > > On Fri, Sep 20, 2019 at 4:02 PM Dawid Wysakowicz > > > wrote: > > > > > I also like the 'System' keyword. I think we can assume we reached > > > consensus on this topic. > > > > > > On Sat, 21 Sep 2019, 06:37 Xuefu Z, wrote: > > > > > > > +1 for using the keyword "SYSTEM". Thanks to Timo for chiming in! > > > > > > > > --Xuefu > > > > > > > > On Fri, Sep 20, 2019 at 3:28 PM Timo Walther > > wrote: > > > > > > > > > Hi everyone, > > > > > > > > > > sorry, for the late replay. I give also +1 for option #2. Thus, I > > guess > > > > > we have a clear winner. > > > > > > > > > > I would also like to find a better keyword/syntax for this > statement. > > > > > Esp. the BUILTIN keyword can confuse people, because it could be > > > written > > > > > as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to > > > > > introduce a new reserved keyword in the parser which affects also > > > > > non-DDL queries. How about: > > > > > > > > > > CREATE TEMPORARY SYSTEM FUNCTION xxx > > > > > > > > > > The SYSTEM keyword is already a reserved keyword and in FLIP-66 we > > are > > > > > discussing to prefix some of the function with a SYSTEM_ prefix > like > > > > > SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS > > OF". > > > > > > > > > > What do you think? > > > > > > > > > > Thanks, > > > > > Timo > > > > > > > > > > > > > > > On 20.09.19 05:45, Bowen Li wrote: > > > > > > Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over > > > "ALTER > > > > > > BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop > > the > > > > > > temporary built-in function in the same session? With the former > > one, > > > > > they > > > > > > can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With > the > > > > latter > > > > > > one, I'm not sure how users can "restore" the original builtin > > > function > > > > > > easily from an "altered" function without introducing further > > > > nonstandard > > > > > > SQL syntax. > > > > > > > > > > > > Also please pardon me as I realized using net may not be a good > > > idea... > > > > > I'm > > > > > > trying to fit this vote into cases listed in Flink Bylaw [1]. > > > > > > > > > > > > >From the following result, the majority seems to be #2 too as it > > has > > > > the > > > > > > most approval so far and doesn't have strong "-1". > > > > > > > > > > > > #1：3 (+1), 1 (0), 4(-1) > > > > > > #2：4(0), 3 (+1), 1(+0.5) > > > > > > * Dawid -1/0 depending on keyword > > > > > > #3：2(+1), 3(-1), 3(0) > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > > > > > > > > > On Thu, Sep 19, 2019 at 10:30 AM Bowen Li > > > wrote: > > > > > > > > > > > >> Hi, > > > > > >> > > > > > >> Thanks everyone for your votes. I summarized the result as > > > following: > > > > > >> > > > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > > > >> #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > > > > > >> Dawid -1/0 depending on keyword > > > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > > > >> > > > > > >> Given the result, I'd like to change my vote for #2 from 0 to > +1, > > to > > > > > make > > > > > >> it a stronger case with net +3.5. So the votes so far are: > > > > > >> > > > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > > > >> #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > > > > > >> Dawid -1/0 depending on keyword > > > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > > > >> > > > > > >> What do you think? Do you think we can conclude with this > result? > > Or > > > > > would > > > > > >> you like to take it as a formal FLIP vote with 3 days voting > > period? > > > > > >> > > > > > >> BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > > > > BUILTIN > > > > > >> FUNCTION xxx TEMPORARILY" because > > > > > >> 1. the syntax is more consistent with "CREATE FUNCTION" and > > "CREATE > > > > > >> TEMPORARY FUNCTION" > > > > > >> 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a > > > > built-in > > > > > >> function but it actually doesn't, the logic only creates a temp > > > > function > > > > > >> with higher priority than that built-in function in ambiguous > > > > resolution > > > > > >> order; and it would behave inconsistently with "ALTER FUNCTION". > > > > > >> > > > > > >> > > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
+1 for CREATE TEMPORARY SYSTEM FUNCTION xxx Cheers, Fabian Am Sa., 21. Sept. 2019 um 06:58 Uhr schrieb Bowen Li : > "SYSTEM" sounds good to me. FYI, this FLIP only impacts low level of the > SQL function stack and won't actually involve any DDL, thus I will just > document the decision and we should keep it in mind when it's time to > implement the DDLs. > > I'm in the process of updating the FLIP to reflect changes required for > option #2, will send a new version for review soon. > > > > On Fri, Sep 20, 2019 at 4:02 PM Dawid Wysakowicz > wrote: > > > I also like the 'System' keyword. I think we can assume we reached > > consensus on this topic. > > > > On Sat, 21 Sep 2019, 06:37 Xuefu Z, wrote: > > > > > +1 for using the keyword "SYSTEM". Thanks to Timo for chiming in! > > > > > > --Xuefu > > > > > > On Fri, Sep 20, 2019 at 3:28 PM Timo Walther > wrote: > > > > > > > Hi everyone, > > > > > > > > sorry, for the late replay. I give also +1 for option #2. Thus, I > guess > > > > we have a clear winner. > > > > > > > > I would also like to find a better keyword/syntax for this statement. > > > > Esp. the BUILTIN keyword can confuse people, because it could be > > written > > > > as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to > > > > introduce a new reserved keyword in the parser which affects also > > > > non-DDL queries. How about: > > > > > > > > CREATE TEMPORARY SYSTEM FUNCTION xxx > > > > > > > > The SYSTEM keyword is already a reserved keyword and in FLIP-66 we > are > > > > discussing to prefix some of the function with a SYSTEM_ prefix like > > > > SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS > OF". > > > > > > > > What do you think? > > > > > > > > Thanks, > > > > Timo > > > > > > > > > > > > On 20.09.19 05:45, Bowen Li wrote: > > > > > Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over > > "ALTER > > > > > BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop > the > > > > > temporary built-in function in the same session? With the former > one, > > > > they > > > > > can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the > > > latter > > > > > one, I'm not sure how users can "restore" the original builtin > > function > > > > > easily from an "altered" function without introducing further > > > nonstandard > > > > > SQL syntax. > > > > > > > > > > Also please pardon me as I realized using net may not be a good > > idea... > > > > I'm > > > > > trying to fit this vote into cases listed in Flink Bylaw [1]. > > > > > > > > > > >From the following result, the majority seems to be #2 too as it > has > > > the > > > > > most approval so far and doesn't have strong "-1". > > > > > > > > > > #1：3 (+1), 1 (0), 4(-1) > > > > > #2：4(0), 3 (+1), 1(+0.5) > > > > > * Dawid -1/0 depending on keyword > > > > > #3：2(+1), 3(-1), 3(0) > > > > > > > > > > [1] > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > > > > > > > On Thu, Sep 19, 2019 at 10:30 AM Bowen Li > > wrote: > > > > > > > > > >> Hi, > > > > >> > > > > >> Thanks everyone for your votes. I summarized the result as > > following: > > > > >> > > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > > >> #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > > > > >> Dawid -1/0 depending on keyword > > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > > >> > > > > >> Given the result, I'd like to change my vote for #2 from 0 to +1, > to > > > > make > > > > >> it a stronger case with net +3.5. So the votes so far are: > > > > >> > > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > > >> #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > > > > >> Dawid -1/0 depending on keyword > > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > > >> > > > > >> What do you think? Do you think we can conclude with this result? > Or > > > > would > > > > >> you like to take it as a formal FLIP vote with 3 days voting > period? > > > > >> > > > > >> BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > > > BUILTIN > > > > >> FUNCTION xxx TEMPORARILY" because > > > > >> 1. the syntax is more consistent with "CREATE FUNCTION" and > "CREATE > > > > >> TEMPORARY FUNCTION" > > > > >> 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a > > > built-in > > > > >> function but it actually doesn't, the logic only creates a temp > > > function > > > > >> with higher priority than that built-in function in ambiguous > > > resolution > > > > >> order; and it would behave inconsistently with "ALTER FUNCTION". > > > > >> > > > > >> > > > > >> > > > > >> On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske > > > > wrote: > > > > >> > > > > >>> I agree, it's very similar from the implementation point of view > > and > > > > the > > > > >>> implications. > > > > >>> > > > > >>> IMO, the difference is mostly on the mental model for the user. > > > > >>> Instead of having a special class of temporary functions that > have > > > > >>>
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
"SYSTEM" sounds good to me. FYI, this FLIP only impacts low level of the SQL function stack and won't actually involve any DDL, thus I will just document the decision and we should keep it in mind when it's time to implement the DDLs. I'm in the process of updating the FLIP to reflect changes required for option #2, will send a new version for review soon. On Fri, Sep 20, 2019 at 4:02 PM Dawid Wysakowicz wrote: > I also like the 'System' keyword. I think we can assume we reached > consensus on this topic. > > On Sat, 21 Sep 2019, 06:37 Xuefu Z, wrote: > > > +1 for using the keyword "SYSTEM". Thanks to Timo for chiming in! > > > > --Xuefu > > > > On Fri, Sep 20, 2019 at 3:28 PM Timo Walther wrote: > > > > > Hi everyone, > > > > > > sorry, for the late replay. I give also +1 for option #2. Thus, I guess > > > we have a clear winner. > > > > > > I would also like to find a better keyword/syntax for this statement. > > > Esp. the BUILTIN keyword can confuse people, because it could be > written > > > as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to > > > introduce a new reserved keyword in the parser which affects also > > > non-DDL queries. How about: > > > > > > CREATE TEMPORARY SYSTEM FUNCTION xxx > > > > > > The SYSTEM keyword is already a reserved keyword and in FLIP-66 we are > > > discussing to prefix some of the function with a SYSTEM_ prefix like > > > SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS OF". > > > > > > What do you think? > > > > > > Thanks, > > > Timo > > > > > > > > > On 20.09.19 05:45, Bowen Li wrote: > > > > Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over > "ALTER > > > > BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop the > > > > temporary built-in function in the same session? With the former one, > > > they > > > > can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the > > latter > > > > one, I'm not sure how users can "restore" the original builtin > function > > > > easily from an "altered" function without introducing further > > nonstandard > > > > SQL syntax. > > > > > > > > Also please pardon me as I realized using net may not be a good > idea... > > > I'm > > > > trying to fit this vote into cases listed in Flink Bylaw [1]. > > > > > > > > >From the following result, the majority seems to be #2 too as it has > > the > > > > most approval so far and doesn't have strong "-1". > > > > > > > > #1：3 (+1), 1 (0), 4(-1) > > > > #2：4(0), 3 (+1), 1(+0.5) > > > > * Dawid -1/0 depending on keyword > > > > #3：2(+1), 3(-1), 3(0) > > > > > > > > [1] > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > > > > > On Thu, Sep 19, 2019 at 10:30 AM Bowen Li > wrote: > > > > > > > >> Hi, > > > >> > > > >> Thanks everyone for your votes. I summarized the result as > following: > > > >> > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > >> #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > > > >> Dawid -1/0 depending on keyword > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > >> > > > >> Given the result, I'd like to change my vote for #2 from 0 to +1, to > > > make > > > >> it a stronger case with net +3.5. So the votes so far are: > > > >> > > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > > >> #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > > > >> Dawid -1/0 depending on keyword > > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > > >> > > > >> What do you think? Do you think we can conclude with this result? Or > > > would > > > >> you like to take it as a formal FLIP vote with 3 days voting period? > > > >> > > > >> BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > > BUILTIN > > > >> FUNCTION xxx TEMPORARILY" because > > > >> 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE > > > >> TEMPORARY FUNCTION" > > > >> 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a > > built-in > > > >> function but it actually doesn't, the logic only creates a temp > > function > > > >> with higher priority than that built-in function in ambiguous > > resolution > > > >> order; and it would behave inconsistently with "ALTER FUNCTION". > > > >> > > > >> > > > >> > > > >> On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske > > > wrote: > > > >> > > > >>> I agree, it's very similar from the implementation point of view > and > > > the > > > >>> implications. > > > >>> > > > >>> IMO, the difference is mostly on the mental model for the user. > > > >>> Instead of having a special class of temporary functions that have > > > >>> precedence over builtin functions it suggests to temporarily change > > > >>> built-in functions. > > > >>> > > > >>> Fabian > > > >>> > > > >>> Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young < > > > ykt...@gmail.com > > > : > > > Hi Fabian, > > > > > > I think it's almost the same with #2 with different keyword: > > > > > > CREATE TEMPORARY BUILTIN FUNCTION xxx >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
I also like the 'System' keyword. I think we can assume we reached consensus on this topic. On Sat, 21 Sep 2019, 06:37 Xuefu Z, wrote: > +1 for using the keyword "SYSTEM". Thanks to Timo for chiming in! > > --Xuefu > > On Fri, Sep 20, 2019 at 3:28 PM Timo Walther wrote: > > > Hi everyone, > > > > sorry, for the late replay. I give also +1 for option #2. Thus, I guess > > we have a clear winner. > > > > I would also like to find a better keyword/syntax for this statement. > > Esp. the BUILTIN keyword can confuse people, because it could be written > > as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to > > introduce a new reserved keyword in the parser which affects also > > non-DDL queries. How about: > > > > CREATE TEMPORARY SYSTEM FUNCTION xxx > > > > The SYSTEM keyword is already a reserved keyword and in FLIP-66 we are > > discussing to prefix some of the function with a SYSTEM_ prefix like > > SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS OF". > > > > What do you think? > > > > Thanks, > > Timo > > > > > > On 20.09.19 05:45, Bowen Li wrote: > > > Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > > > BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop the > > > temporary built-in function in the same session? With the former one, > > they > > > can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the > latter > > > one, I'm not sure how users can "restore" the original builtin function > > > easily from an "altered" function without introducing further > nonstandard > > > SQL syntax. > > > > > > Also please pardon me as I realized using net may not be a good idea... > > I'm > > > trying to fit this vote into cases listed in Flink Bylaw [1]. > > > > > > >From the following result, the majority seems to be #2 too as it has > the > > > most approval so far and doesn't have strong "-1". > > > > > > #1：3 (+1), 1 (0), 4(-1) > > > #2：4(0), 3 (+1), 1(+0.5) > > > * Dawid -1/0 depending on keyword > > > #3：2(+1), 3(-1), 3(0) > > > > > > [1] > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > > > On Thu, Sep 19, 2019 at 10:30 AM Bowen Li wrote: > > > > > >> Hi, > > >> > > >> Thanks everyone for your votes. I summarized the result as following: > > >> > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > >> #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > > >> Dawid -1/0 depending on keyword > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > >> > > >> Given the result, I'd like to change my vote for #2 from 0 to +1, to > > make > > >> it a stronger case with net +3.5. So the votes so far are: > > >> > > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > > >> #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > > >> Dawid -1/0 depending on keyword > > >> #3：2(+1), 3(-1), 3(0) - net: -1 > > >> > > >> What do you think? Do you think we can conclude with this result? Or > > would > > >> you like to take it as a formal FLIP vote with 3 days voting period? > > >> > > >> BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > BUILTIN > > >> FUNCTION xxx TEMPORARILY" because > > >> 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE > > >> TEMPORARY FUNCTION" > > >> 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a > built-in > > >> function but it actually doesn't, the logic only creates a temp > function > > >> with higher priority than that built-in function in ambiguous > resolution > > >> order; and it would behave inconsistently with "ALTER FUNCTION". > > >> > > >> > > >> > > >> On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske > > wrote: > > >> > > >>> I agree, it's very similar from the implementation point of view and > > the > > >>> implications. > > >>> > > >>> IMO, the difference is mostly on the mental model for the user. > > >>> Instead of having a special class of temporary functions that have > > >>> precedence over builtin functions it suggests to temporarily change > > >>> built-in functions. > > >>> > > >>> Fabian > > >>> > > >>> Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young < > > ykt...@gmail.com > > : > > Hi Fabian, > > > > I think it's almost the same with #2 with different keyword: > > > > CREATE TEMPORARY BUILTIN FUNCTION xxx > > > > Best, > > Kurt > > > > > > On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske > > >>> wrote: > > > Hi, > > > > > > I thought about it a bit more and think that there is some good > value > > >>> in > > my > > > last proposal. > > > > > > A lot of complexity comes from the fact that we want to allow > > >>> overriding > > > built-in functions which are differently addressed as other > functions > > (and > > > db objects). > > > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same > > >>> thing > > as > > > "CREATE FUNCTION" and treat both functions exactly the same except > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
+1 for using the keyword "SYSTEM". Thanks to Timo for chiming in! --Xuefu On Fri, Sep 20, 2019 at 3:28 PM Timo Walther wrote: > Hi everyone, > > sorry, for the late replay. I give also +1 for option #2. Thus, I guess > we have a clear winner. > > I would also like to find a better keyword/syntax for this statement. > Esp. the BUILTIN keyword can confuse people, because it could be written > as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to > introduce a new reserved keyword in the parser which affects also > non-DDL queries. How about: > > CREATE TEMPORARY SYSTEM FUNCTION xxx > > The SYSTEM keyword is already a reserved keyword and in FLIP-66 we are > discussing to prefix some of the function with a SYSTEM_ prefix like > SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS OF". > > What do you think? > > Thanks, > Timo > > > On 20.09.19 05:45, Bowen Li wrote: > > Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER > > BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop the > > temporary built-in function in the same session? With the former one, > they > > can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the latter > > one, I'm not sure how users can "restore" the original builtin function > > easily from an "altered" function without introducing further nonstandard > > SQL syntax. > > > > Also please pardon me as I realized using net may not be a good idea... > I'm > > trying to fit this vote into cases listed in Flink Bylaw [1]. > > > > >From the following result, the majority seems to be #2 too as it has the > > most approval so far and doesn't have strong "-1". > > > > #1：3 (+1), 1 (0), 4(-1) > > #2：4(0), 3 (+1), 1(+0.5) > > * Dawid -1/0 depending on keyword > > #3：2(+1), 3(-1), 3(0) > > > > [1] > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > On Thu, Sep 19, 2019 at 10:30 AM Bowen Li wrote: > > > >> Hi, > >> > >> Thanks everyone for your votes. I summarized the result as following: > >> > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > >> #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > >> Dawid -1/0 depending on keyword > >> #3：2(+1), 3(-1), 3(0) - net: -1 > >> > >> Given the result, I'd like to change my vote for #2 from 0 to +1, to > make > >> it a stronger case with net +3.5. So the votes so far are: > >> > >> #1：3 (+1), 1 (0), 4(-1) - net: -1 > >> #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > >> Dawid -1/0 depending on keyword > >> #3：2(+1), 3(-1), 3(0) - net: -1 > >> > >> What do you think? Do you think we can conclude with this result? Or > would > >> you like to take it as a formal FLIP vote with 3 days voting period? > >> > >> BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN > >> FUNCTION xxx TEMPORARILY" because > >> 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE > >> TEMPORARY FUNCTION" > >> 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a built-in > >> function but it actually doesn't, the logic only creates a temp function > >> with higher priority than that built-in function in ambiguous resolution > >> order; and it would behave inconsistently with "ALTER FUNCTION". > >> > >> > >> > >> On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske > wrote: > >> > >>> I agree, it's very similar from the implementation point of view and > the > >>> implications. > >>> > >>> IMO, the difference is mostly on the mental model for the user. > >>> Instead of having a special class of temporary functions that have > >>> precedence over builtin functions it suggests to temporarily change > >>> built-in functions. > >>> > >>> Fabian > >>> > >>> Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young < > ykt...@gmail.com > : > Hi Fabian, > > I think it's almost the same with #2 with different keyword: > > CREATE TEMPORARY BUILTIN FUNCTION xxx > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske > >>> wrote: > > Hi, > > > > I thought about it a bit more and think that there is some good value > >>> in > my > > last proposal. > > > > A lot of complexity comes from the fact that we want to allow > >>> overriding > > built-in functions which are differently addressed as other functions > (and > > db objects). > > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same > >>> thing > as > > "CREATE FUNCTION" and treat both functions exactly the same except > >>> that: > > 1) temp functions disappear at the end of the session > > 2) temp function are resolved before other functions > > > > This would be Dawid's proposal from the beginning of this thread (in > >>> case > > you still remember... ;-) ) > > > > Temporarily overriding built-in functions would be supported with an > > explicit command like > > > > ALTER BUILTIN FUNCTION xxx
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi everyone, sorry, for the late replay. I give also +1 for option #2. Thus, I guess we have a clear winner. I would also like to find a better keyword/syntax for this statement. Esp. the BUILTIN keyword can confuse people, because it could be written as BUILTIN, BUILDIN, BUILT_IN, or BUILD_IN. And we would need to introduce a new reserved keyword in the parser which affects also non-DDL queries. How about: CREATE TEMPORARY SYSTEM FUNCTION xxx The SYSTEM keyword is already a reserved keyword and in FLIP-66 we are discussing to prefix some of the function with a SYSTEM_ prefix like SYSTEM_WATERMARK. Also SQL defines syntax like "FOR SYSTEM_TIME AS OF". What do you think? Thanks, Timo On 20.09.19 05:45, Bowen Li wrote: Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop the temporary built-in function in the same session? With the former one, they can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the latter one, I'm not sure how users can "restore" the original builtin function easily from an "altered" function without introducing further nonstandard SQL syntax. Also please pardon me as I realized using net may not be a good idea... I'm trying to fit this vote into cases listed in Flink Bylaw [1]. >From the following result, the majority seems to be #2 too as it has the most approval so far and doesn't have strong "-1". #1：3 (+1), 1 (0), 4(-1) #2：4(0), 3 (+1), 1(+0.5) * Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) [1] https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 On Thu, Sep 19, 2019 at 10:30 AM Bowen Li wrote: Hi, Thanks everyone for your votes. I summarized the result as following: #1：3 (+1), 1 (0), 4(-1) - net: -1 #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) - net: -1 Given the result, I'd like to change my vote for #2 from 0 to +1, to make it a stronger case with net +3.5. So the votes so far are: #1：3 (+1), 1 (0), 4(-1) - net: -1 #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) - net: -1 What do you think? Do you think we can conclude with this result? Or would you like to take it as a formal FLIP vote with 3 days voting period? BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN FUNCTION xxx TEMPORARILY" because 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE TEMPORARY FUNCTION" 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a built-in function but it actually doesn't, the logic only creates a temp function with higher priority than that built-in function in ambiguous resolution order; and it would behave inconsistently with "ALTER FUNCTION". On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske wrote: I agree, it's very similar from the implementation point of view and the implications. IMO, the difference is mostly on the mental model for the user. Instead of having a special class of temporary functions that have precedence over builtin functions it suggests to temporarily change built-in functions. Fabian Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young : Hi Fabian, I think it's almost the same with #2 with different keyword: CREATE TEMPORARY BUILTIN FUNCTION xxx Best, Kurt On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske wrote: Hi, I thought about it a bit more and think that there is some good value in my last proposal. A lot of complexity comes from the fact that we want to allow overriding built-in functions which are differently addressed as other functions (and db objects). We could just have "CREATE TEMPORARY FUNCTION" do exactly the same thing as "CREATE FUNCTION" and treat both functions exactly the same except that: 1) temp functions disappear at the end of the session 2) temp function are resolved before other functions This would be Dawid's proposal from the beginning of this thread (in case you still remember... ;-) ) Temporarily overriding built-in functions would be supported with an explicit command like ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... This would also address the concerns about accidentally changing the semantics of built-in functions. IMO, it can't get much more explicit than the above command. Sorry for bringing up a new option in the middle of the discussion, but as I said, I think it has a bunch of benefits and I don't see major drawbacks (maybe you do?). What do you think? Fabian Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske < fhue...@gmail.com : Hi everyone, I thought again about option #1 and something that I don't like is that the resolved address of xyz is different in "CREATE FUNCTION xyz" and "CREATE TEMPORARY FUNCTION xyz". IMO, adding the keyword "TEMPORARY" should only change the lifecycle of the function, but not where it is located.
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Another reason I prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN FUNCTION xxx TEMPORARILY" is - what if users want to drop the temporary built-in function in the same session? With the former one, they can run something like "DROP TEMPORARY BUILTIN FUNCTION"; With the latter one, I'm not sure how users can "restore" the original builtin function easily from an "altered" function without introducing further nonstandard SQL syntax. Also please pardon me as I realized using net may not be a good idea... I'm trying to fit this vote into cases listed in Flink Bylaw [1]. >From the following result, the majority seems to be #2 too as it has the most approval so far and doesn't have strong "-1". #1：3 (+1), 1 (0), 4(-1) #2：4(0), 3 (+1), 1(+0.5) * Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) [1] https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 On Thu, Sep 19, 2019 at 10:30 AM Bowen Li wrote: > Hi, > > Thanks everyone for your votes. I summarized the result as following: > > #1：3 (+1), 1 (0), 4(-1) - net: -1 > #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 > Dawid -1/0 depending on keyword > #3：2(+1), 3(-1), 3(0) - net: -1 > > Given the result, I'd like to change my vote for #2 from 0 to +1, to make > it a stronger case with net +3.5. So the votes so far are: > > #1：3 (+1), 1 (0), 4(-1) - net: -1 > #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 > Dawid -1/0 depending on keyword > #3：2(+1), 3(-1), 3(0) - net: -1 > > What do you think? Do you think we can conclude with this result? Or would > you like to take it as a formal FLIP vote with 3 days voting period? > > BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN > FUNCTION xxx TEMPORARILY" because > 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE > TEMPORARY FUNCTION" > 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a built-in > function but it actually doesn't, the logic only creates a temp function > with higher priority than that built-in function in ambiguous resolution > order; and it would behave inconsistently with "ALTER FUNCTION". > > > > On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske wrote: > >> I agree, it's very similar from the implementation point of view and the >> implications. >> >> IMO, the difference is mostly on the mental model for the user. >> Instead of having a special class of temporary functions that have >> precedence over builtin functions it suggests to temporarily change >> built-in functions. >> >> Fabian >> >> Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young > >: >> >> > Hi Fabian, >> > >> > I think it's almost the same with #2 with different keyword: >> > >> > CREATE TEMPORARY BUILTIN FUNCTION xxx >> > >> > Best, >> > Kurt >> > >> > >> > On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske >> wrote: >> > >> > > Hi, >> > > >> > > I thought about it a bit more and think that there is some good value >> in >> > my >> > > last proposal. >> > > >> > > A lot of complexity comes from the fact that we want to allow >> overriding >> > > built-in functions which are differently addressed as other functions >> > (and >> > > db objects). >> > > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same >> thing >> > as >> > > "CREATE FUNCTION" and treat both functions exactly the same except >> that: >> > > 1) temp functions disappear at the end of the session >> > > 2) temp function are resolved before other functions >> > > >> > > This would be Dawid's proposal from the beginning of this thread (in >> case >> > > you still remember... ;-) ) >> > > >> > > Temporarily overriding built-in functions would be supported with an >> > > explicit command like >> > > >> > > ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... >> > > >> > > This would also address the concerns about accidentally changing the >> > > semantics of built-in functions. >> > > IMO, it can't get much more explicit than the above command. >> > > >> > > Sorry for bringing up a new option in the middle of the discussion, >> but >> > as >> > > I said, I think it has a bunch of benefits and I don't see major >> > drawbacks >> > > (maybe you do?). >> > > >> > > What do you think? >> > > >> > > Fabian >> > > >> > > Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske < >> > > fhue...@gmail.com >> > > >: >> > > >> > > > Hi everyone, >> > > > >> > > > I thought again about option #1 and something that I don't like is >> that >> > > > the resolved address of xyz is different in "CREATE FUNCTION xyz" >> and >> > > > "CREATE TEMPORARY FUNCTION xyz". >> > > > IMO, adding the keyword "TEMPORARY" should only change the >> lifecycle of >> > > > the function, but not where it is located. This implicitly changed >> > > location >> > > > might be confusing for users. >> > > > After all, a temp function should behave pretty much like any other >> > > > function, except for the fact that it disappears when the session is >> > > closed. >> > > > >> > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, Thanks everyone for your votes. I summarized the result as following: #1：3 (+1), 1 (0), 4(-1) - net: -1 #2：4(0), 2 (+1), 1(+0.5) - net: +2.5 Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) - net: -1 Given the result, I'd like to change my vote for #2 from 0 to +1, to make it a stronger case with net +3.5. So the votes so far are: #1：3 (+1), 1 (0), 4(-1) - net: -1 #2：4(0), 3 (+1), 1(+0.5) - net: +3.5 Dawid -1/0 depending on keyword #3：2(+1), 3(-1), 3(0) - net: -1 What do you think? Do you think we can conclude with this result? Or would you like to take it as a formal FLIP vote with 3 days voting period? BTW, I'd prefer "CREATE TEMPORARY BUILTIN FUNCTION" over "ALTER BUILTIN FUNCTION xxx TEMPORARILY" because 1. the syntax is more consistent with "CREATE FUNCTION" and "CREATE TEMPORARY FUNCTION" 2. "ALTER BUILTIN FUNCTION xxx TEMPORARILY" implies it alters a built-in function but it actually doesn't, the logic only creates a temp function with higher priority than that built-in function in ambiguous resolution order; and it would behave inconsistently with "ALTER FUNCTION". On Thu, Sep 19, 2019 at 2:58 AM Fabian Hueske wrote: > I agree, it's very similar from the implementation point of view and the > implications. > > IMO, the difference is mostly on the mental model for the user. > Instead of having a special class of temporary functions that have > precedence over builtin functions it suggests to temporarily change > built-in functions. > > Fabian > > Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young : > > > Hi Fabian, > > > > I think it's almost the same with #2 with different keyword: > > > > CREATE TEMPORARY BUILTIN FUNCTION xxx > > > > Best, > > Kurt > > > > > > On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske wrote: > > > > > Hi, > > > > > > I thought about it a bit more and think that there is some good value > in > > my > > > last proposal. > > > > > > A lot of complexity comes from the fact that we want to allow > overriding > > > built-in functions which are differently addressed as other functions > > (and > > > db objects). > > > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same > thing > > as > > > "CREATE FUNCTION" and treat both functions exactly the same except > that: > > > 1) temp functions disappear at the end of the session > > > 2) temp function are resolved before other functions > > > > > > This would be Dawid's proposal from the beginning of this thread (in > case > > > you still remember... ;-) ) > > > > > > Temporarily overriding built-in functions would be supported with an > > > explicit command like > > > > > > ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... > > > > > > This would also address the concerns about accidentally changing the > > > semantics of built-in functions. > > > IMO, it can't get much more explicit than the above command. > > > > > > Sorry for bringing up a new option in the middle of the discussion, but > > as > > > I said, I think it has a bunch of benefits and I don't see major > > drawbacks > > > (maybe you do?). > > > > > > What do you think? > > > > > > Fabian > > > > > > Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske < > > > fhue...@gmail.com > > > >: > > > > > > > Hi everyone, > > > > > > > > I thought again about option #1 and something that I don't like is > that > > > > the resolved address of xyz is different in "CREATE FUNCTION xyz" and > > > > "CREATE TEMPORARY FUNCTION xyz". > > > > IMO, adding the keyword "TEMPORARY" should only change the lifecycle > of > > > > the function, but not where it is located. This implicitly changed > > > location > > > > might be confusing for users. > > > > After all, a temp function should behave pretty much like any other > > > > function, except for the fact that it disappears when the session is > > > closed. > > > > > > > > Approach #2 with the additional keyword would make that pretty clear, > > > IMO. > > > > However, I neither like GLOBAL (for reasons mentioned by Dawid) or > > > BUILDIN > > > > (we are not adding a built-in function). > > > > So I'd be OK with #2 if we find a good keyword. In fact, approach #2 > > > could > > > > also be an alias for approach #3 to avoid explicit specification of > the > > > > system catalog/db. > > > > > > > > Approach #3 would be consistent with other db objects and the "CREATE > > > > FUNCTION" statement. > > > > Adding system catalog/db seems rather complex, but then again how > often > > > do > > > > we expect users to override built-in functions? If this becomes a > major > > > > issue, we can still add option #2 as an alias. > > > > > > > > Not sure what's the best approach from an internal point of view, > but I > > > > certainly think that consistent behavior is important. > > > > Hence my votes are: > > > > > > > > -1 for #1 > > > > 0 for #2 > > > > 0 for #3 > > > > > > > > Btw. Did we consider a completely separate command for overriding > > > built-in > > > > functions
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
I agree, it's very similar from the implementation point of view and the implications. IMO, the difference is mostly on the mental model for the user. Instead of having a special class of temporary functions that have precedence over builtin functions it suggests to temporarily change built-in functions. Fabian Am Do., 19. Sept. 2019 um 11:52 Uhr schrieb Kurt Young : > Hi Fabian, > > I think it's almost the same with #2 with different keyword: > > CREATE TEMPORARY BUILTIN FUNCTION xxx > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske wrote: > > > Hi, > > > > I thought about it a bit more and think that there is some good value in > my > > last proposal. > > > > A lot of complexity comes from the fact that we want to allow overriding > > built-in functions which are differently addressed as other functions > (and > > db objects). > > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same thing > as > > "CREATE FUNCTION" and treat both functions exactly the same except that: > > 1) temp functions disappear at the end of the session > > 2) temp function are resolved before other functions > > > > This would be Dawid's proposal from the beginning of this thread (in case > > you still remember... ;-) ) > > > > Temporarily overriding built-in functions would be supported with an > > explicit command like > > > > ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... > > > > This would also address the concerns about accidentally changing the > > semantics of built-in functions. > > IMO, it can't get much more explicit than the above command. > > > > Sorry for bringing up a new option in the middle of the discussion, but > as > > I said, I think it has a bunch of benefits and I don't see major > drawbacks > > (maybe you do?). > > > > What do you think? > > > > Fabian > > > > Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske < > > fhue...@gmail.com > > >: > > > > > Hi everyone, > > > > > > I thought again about option #1 and something that I don't like is that > > > the resolved address of xyz is different in "CREATE FUNCTION xyz" and > > > "CREATE TEMPORARY FUNCTION xyz". > > > IMO, adding the keyword "TEMPORARY" should only change the lifecycle of > > > the function, but not where it is located. This implicitly changed > > location > > > might be confusing for users. > > > After all, a temp function should behave pretty much like any other > > > function, except for the fact that it disappears when the session is > > closed. > > > > > > Approach #2 with the additional keyword would make that pretty clear, > > IMO. > > > However, I neither like GLOBAL (for reasons mentioned by Dawid) or > > BUILDIN > > > (we are not adding a built-in function). > > > So I'd be OK with #2 if we find a good keyword. In fact, approach #2 > > could > > > also be an alias for approach #3 to avoid explicit specification of the > > > system catalog/db. > > > > > > Approach #3 would be consistent with other db objects and the "CREATE > > > FUNCTION" statement. > > > Adding system catalog/db seems rather complex, but then again how often > > do > > > we expect users to override built-in functions? If this becomes a major > > > issue, we can still add option #2 as an alias. > > > > > > Not sure what's the best approach from an internal point of view, but I > > > certainly think that consistent behavior is important. > > > Hence my votes are: > > > > > > -1 for #1 > > > 0 for #2 > > > 0 for #3 > > > > > > Btw. Did we consider a completely separate command for overriding > > built-in > > > functions like "ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ..."? > > > > > > Cheers, Fabian > > > > > > > > > Am Do., 19. Sept. 2019 um 11:03 Uhr schrieb JingsongLee > > > : > > > > > >> I know Hive and Spark can shadow built-in functions by temporary > > function. > > >> Mysql, Oracle, Sql server can not shadow. > > >> User can use full names to access functions instead of shadowing. > > >> > > >> So I think it is a completely new thing, and the direct way to deal > with > > >> new things is to add new grammar. So, > > >> +1 for #2, +0 for #3, -1 for #1 > > >> > > >> Best, > > >> Jingsong Lee > > >> > > >> > > >> -- > > >> From:Kurt Young > > >> Send Time:2019年9月19日(星期四) 16:43 > > >> To:dev > > >> Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog > > >> > > >> And let me make my vote complete: > > >> > > >> -1 for #1 > > >> +1 for #2 with different keyword > > >> -0 for #3 > > >> > > >> Best, > > >> Kurt > > >> > > >> > > >> On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > > >> > > >> > Looks like I'm the only person who is willing to +1 to #2 for now > :-) > > >> > But I would suggest to change the keyword from GLOBAL to > > >> > something like BUILTIN. > > >> > > > >> > I think #2 and #3 are almost the same proposal, just with different > > >> > format to indicate whether it want to override built-in functions. > > >> > > > >> > My biggest
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Fabian, I think it's almost the same with #2 with different keyword: CREATE TEMPORARY BUILTIN FUNCTION xxx Best, Kurt On Thu, Sep 19, 2019 at 5:50 PM Fabian Hueske wrote: > Hi, > > I thought about it a bit more and think that there is some good value in my > last proposal. > > A lot of complexity comes from the fact that we want to allow overriding > built-in functions which are differently addressed as other functions (and > db objects). > We could just have "CREATE TEMPORARY FUNCTION" do exactly the same thing as > "CREATE FUNCTION" and treat both functions exactly the same except that: > 1) temp functions disappear at the end of the session > 2) temp function are resolved before other functions > > This would be Dawid's proposal from the beginning of this thread (in case > you still remember... ;-) ) > > Temporarily overriding built-in functions would be supported with an > explicit command like > > ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... > > This would also address the concerns about accidentally changing the > semantics of built-in functions. > IMO, it can't get much more explicit than the above command. > > Sorry for bringing up a new option in the middle of the discussion, but as > I said, I think it has a bunch of benefits and I don't see major drawbacks > (maybe you do?). > > What do you think? > > Fabian > > Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske < > fhue...@gmail.com > >: > > > Hi everyone, > > > > I thought again about option #1 and something that I don't like is that > > the resolved address of xyz is different in "CREATE FUNCTION xyz" and > > "CREATE TEMPORARY FUNCTION xyz". > > IMO, adding the keyword "TEMPORARY" should only change the lifecycle of > > the function, but not where it is located. This implicitly changed > location > > might be confusing for users. > > After all, a temp function should behave pretty much like any other > > function, except for the fact that it disappears when the session is > closed. > > > > Approach #2 with the additional keyword would make that pretty clear, > IMO. > > However, I neither like GLOBAL (for reasons mentioned by Dawid) or > BUILDIN > > (we are not adding a built-in function). > > So I'd be OK with #2 if we find a good keyword. In fact, approach #2 > could > > also be an alias for approach #3 to avoid explicit specification of the > > system catalog/db. > > > > Approach #3 would be consistent with other db objects and the "CREATE > > FUNCTION" statement. > > Adding system catalog/db seems rather complex, but then again how often > do > > we expect users to override built-in functions? If this becomes a major > > issue, we can still add option #2 as an alias. > > > > Not sure what's the best approach from an internal point of view, but I > > certainly think that consistent behavior is important. > > Hence my votes are: > > > > -1 for #1 > > 0 for #2 > > 0 for #3 > > > > Btw. Did we consider a completely separate command for overriding > built-in > > functions like "ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ..."? > > > > Cheers, Fabian > > > > > > Am Do., 19. Sept. 2019 um 11:03 Uhr schrieb JingsongLee > > : > > > >> I know Hive and Spark can shadow built-in functions by temporary > function. > >> Mysql, Oracle, Sql server can not shadow. > >> User can use full names to access functions instead of shadowing. > >> > >> So I think it is a completely new thing, and the direct way to deal with > >> new things is to add new grammar. So, > >> +1 for #2, +0 for #3, -1 for #1 > >> > >> Best, > >> Jingsong Lee > >> > >> > >> -- > >> From:Kurt Young > >> Send Time:2019年9月19日(星期四) 16:43 > >> To:dev > >> Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog > >> > >> And let me make my vote complete: > >> > >> -1 for #1 > >> +1 for #2 with different keyword > >> -0 for #3 > >> > >> Best, > >> Kurt > >> > >> > >> On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > >> > >> > Looks like I'm the only person who is willing to +1 to #2 for now :-) > >> > But I would suggest to change the keyword from GLOBAL to > >> > something like BUILTIN. > >> > > >> > I think #2 and #3 are almost the same proposal, just with different > >> > format to indicate whether it want to override built-in functions. > >> > > >> > My biggest reason to choose it is I want this behavior be consistent > >> > with temporal tables. I will give some examples to show the behavior > >> > and also make sure I'm not misunderstanding anything here. > >> > > >> > For most DBs, when user create a temporary table with: > >> > > >> > CREATE TEMPORARY TABLE t1 > >> > > >> > It's actually equivalent with: > >> > > >> > CREATE TEMPORARY TABLE `curent_db`.t1 > >> > > >> > If user change current database, they will not be able to access t1 > >> without > >> > fully qualified name, .i.e db1.t1 (assuming db1 is current database > when > >> > this temporary table is created). > >> > > >> > Only #2 and #3
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, I thought about it a bit more and think that there is some good value in my last proposal. A lot of complexity comes from the fact that we want to allow overriding built-in functions which are differently addressed as other functions (and db objects). We could just have "CREATE TEMPORARY FUNCTION" do exactly the same thing as "CREATE FUNCTION" and treat both functions exactly the same except that: 1) temp functions disappear at the end of the session 2) temp function are resolved before other functions This would be Dawid's proposal from the beginning of this thread (in case you still remember... ;-) ) Temporarily overriding built-in functions would be supported with an explicit command like ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ... This would also address the concerns about accidentally changing the semantics of built-in functions. IMO, it can't get much more explicit than the above command. Sorry for bringing up a new option in the middle of the discussion, but as I said, I think it has a bunch of benefits and I don't see major drawbacks (maybe you do?). What do you think? Fabian Am Do., 19. Sept. 2019 um 11:24 Uhr schrieb Fabian Hueske : > Hi everyone, > > I thought again about option #1 and something that I don't like is that > the resolved address of xyz is different in "CREATE FUNCTION xyz" and > "CREATE TEMPORARY FUNCTION xyz". > IMO, adding the keyword "TEMPORARY" should only change the lifecycle of > the function, but not where it is located. This implicitly changed location > might be confusing for users. > After all, a temp function should behave pretty much like any other > function, except for the fact that it disappears when the session is closed. > > Approach #2 with the additional keyword would make that pretty clear, IMO. > However, I neither like GLOBAL (for reasons mentioned by Dawid) or BUILDIN > (we are not adding a built-in function). > So I'd be OK with #2 if we find a good keyword. In fact, approach #2 could > also be an alias for approach #3 to avoid explicit specification of the > system catalog/db. > > Approach #3 would be consistent with other db objects and the "CREATE > FUNCTION" statement. > Adding system catalog/db seems rather complex, but then again how often do > we expect users to override built-in functions? If this becomes a major > issue, we can still add option #2 as an alias. > > Not sure what's the best approach from an internal point of view, but I > certainly think that consistent behavior is important. > Hence my votes are: > > -1 for #1 > 0 for #2 > 0 for #3 > > Btw. Did we consider a completely separate command for overriding built-in > functions like "ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ..."? > > Cheers, Fabian > > > Am Do., 19. Sept. 2019 um 11:03 Uhr schrieb JingsongLee > : > >> I know Hive and Spark can shadow built-in functions by temporary function. >> Mysql, Oracle, Sql server can not shadow. >> User can use full names to access functions instead of shadowing. >> >> So I think it is a completely new thing, and the direct way to deal with >> new things is to add new grammar. So, >> +1 for #2, +0 for #3, -1 for #1 >> >> Best, >> Jingsong Lee >> >> >> -- >> From:Kurt Young >> Send Time:2019年9月19日(星期四) 16:43 >> To:dev >> Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog >> >> And let me make my vote complete: >> >> -1 for #1 >> +1 for #2 with different keyword >> -0 for #3 >> >> Best, >> Kurt >> >> >> On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: >> >> > Looks like I'm the only person who is willing to +1 to #2 for now :-) >> > But I would suggest to change the keyword from GLOBAL to >> > something like BUILTIN. >> > >> > I think #2 and #3 are almost the same proposal, just with different >> > format to indicate whether it want to override built-in functions. >> > >> > My biggest reason to choose it is I want this behavior be consistent >> > with temporal tables. I will give some examples to show the behavior >> > and also make sure I'm not misunderstanding anything here. >> > >> > For most DBs, when user create a temporary table with: >> > >> > CREATE TEMPORARY TABLE t1 >> > >> > It's actually equivalent with: >> > >> > CREATE TEMPORARY TABLE `curent_db`.t1 >> > >> > If user change current database, they will not be able to access t1 >> without >> > fully qualified name, .i.e db1.t1 (assuming db1 is current database when >> > this temporary table is created). >> > >> > Only #2 and #3 followed this behavior and I would vote for this since >> this >> > makes such behavior consistent through temporal tables and functions. >> > >> > Why I'm not voting for #3 is a special catalog and database just looks >> very >> > hacky to me. It gave a imply that our built-in functions saved at a >> > special >> > catalog and database, which is actually not. Introducing a dedicated >> > keyword >> > like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and >> >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi everyone, I thought again about option #1 and something that I don't like is that the resolved address of xyz is different in "CREATE FUNCTION xyz" and "CREATE TEMPORARY FUNCTION xyz". IMO, adding the keyword "TEMPORARY" should only change the lifecycle of the function, but not where it is located. This implicitly changed location might be confusing for users. After all, a temp function should behave pretty much like any other function, except for the fact that it disappears when the session is closed. Approach #2 with the additional keyword would make that pretty clear, IMO. However, I neither like GLOBAL (for reasons mentioned by Dawid) or BUILDIN (we are not adding a built-in function). So I'd be OK with #2 if we find a good keyword. In fact, approach #2 could also be an alias for approach #3 to avoid explicit specification of the system catalog/db. Approach #3 would be consistent with other db objects and the "CREATE FUNCTION" statement. Adding system catalog/db seems rather complex, but then again how often do we expect users to override built-in functions? If this becomes a major issue, we can still add option #2 as an alias. Not sure what's the best approach from an internal point of view, but I certainly think that consistent behavior is important. Hence my votes are: -1 for #1 0 for #2 0 for #3 Btw. Did we consider a completely separate command for overriding built-in functions like "ALTER BUILTIN FUNCTION xxx TEMPORARILY AS ..."? Cheers, Fabian Am Do., 19. Sept. 2019 um 11:03 Uhr schrieb JingsongLee : > I know Hive and Spark can shadow built-in functions by temporary function. > Mysql, Oracle, Sql server can not shadow. > User can use full names to access functions instead of shadowing. > > So I think it is a completely new thing, and the direct way to deal with > new things is to add new grammar. So, > +1 for #2, +0 for #3, -1 for #1 > > Best, > Jingsong Lee > > > -- > From:Kurt Young > Send Time:2019年9月19日(星期四) 16:43 > To:dev > Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog > > And let me make my vote complete: > > -1 for #1 > +1 for #2 with different keyword > -0 for #3 > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > > > Looks like I'm the only person who is willing to +1 to #2 for now :-) > > But I would suggest to change the keyword from GLOBAL to > > something like BUILTIN. > > > > I think #2 and #3 are almost the same proposal, just with different > > format to indicate whether it want to override built-in functions. > > > > My biggest reason to choose it is I want this behavior be consistent > > with temporal tables. I will give some examples to show the behavior > > and also make sure I'm not misunderstanding anything here. > > > > For most DBs, when user create a temporary table with: > > > > CREATE TEMPORARY TABLE t1 > > > > It's actually equivalent with: > > > > CREATE TEMPORARY TABLE `curent_db`.t1 > > > > If user change current database, they will not be able to access t1 > without > > fully qualified name, .i.e db1.t1 (assuming db1 is current database when > > this temporary table is created). > > > > Only #2 and #3 followed this behavior and I would vote for this since > this > > makes such behavior consistent through temporal tables and functions. > > > > Why I'm not voting for #3 is a special catalog and database just looks > very > > hacky to me. It gave a imply that our built-in functions saved at a > > special > > catalog and database, which is actually not. Introducing a dedicated > > keyword > > like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and > > straightforward. One can argue that we should avoid introducing new > > keyword, > > but it's also very rare that a system can overwrite built-in functions. > > Since we > > decided to support this, introduce a new keyword is not a big deal IMO. > > > > Best, > > Kurt > > > > > > On Thu, Sep 19, 2019 at 3:07 PM Piotr Nowojski > > wrote: > > > >> Hi, > >> > >> It is a quite long discussion to follow and I hope I didn’t > misunderstand > >> anything. From the proposals presented by Xuefu I would vote: > >> > >> -1 for #1 and #2 > >> +1 for #3 > >> > >> Besides #3 being IMO more general and more consistent, having qualified > >> names (#3) would help/make easier for someone to use cross > >> databases/catalogs queries (joining multiple data sets/streams). For > >> example with some functions to manipulate/clean up/convert the stored > data > >> in different catalogs registered in the respective catalogs. > >> > >> Piotrek > >> > >> > On 19 Sep 2019, at 06:35, Jark Wu wrote: > >> > > >> > I agree with Xuefu that inconsistent handling with all the other > >> objects is > >> > not a big problem. > >> > > >> > Regarding to option#3, the special "system.system" namespace may > confuse > >> > users. > >> > Users need to know the set of built-in function names to know when to > >> use > >> > "system.system"
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
After reading Kurt’s reasoning I’m bumping my vote for #2 from -1 to +0, or even +0.5, so my final vote is: -1 for #1 +0.5 for #2 +1 for #3 Re confusion about “system_db”. I think quite a lot of DBs are storing some meta tables in some system and often hidden db/schema, so I don’t think that if we do the same with built in functions will be that big of a deal. In the end, both for #2 and #3 user will have to check in the documentation what’s the syntax for overriding built-in functions for the first time he will want to do it. Piotrek > On 19 Sep 2019, at 11:03, JingsongLee wrote: > > I know Hive and Spark can shadow built-in functions by temporary function. > Mysql, Oracle, Sql server can not shadow. > User can use full names to access functions instead of shadowing. > > So I think it is a completely new thing, and the direct way to deal with new > things is to add new grammar. So, > +1 for #2, +0 for #3, -1 for #1 > > Best, > Jingsong Lee > > > -- > From:Kurt Young > Send Time:2019年9月19日(星期四) 16:43 > To:dev > Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog > > And let me make my vote complete: > > -1 for #1 > +1 for #2 with different keyword > -0 for #3 > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > >> Looks like I'm the only person who is willing to +1 to #2 for now :-) >> But I would suggest to change the keyword from GLOBAL to >> something like BUILTIN. >> >> I think #2 and #3 are almost the same proposal, just with different >> format to indicate whether it want to override built-in functions. >> >> My biggest reason to choose it is I want this behavior be consistent >> with temporal tables. I will give some examples to show the behavior >> and also make sure I'm not misunderstanding anything here. >> >> For most DBs, when user create a temporary table with: >> >> CREATE TEMPORARY TABLE t1 >> >> It's actually equivalent with: >> >> CREATE TEMPORARY TABLE `curent_db`.t1 >> >> If user change current database, they will not be able to access t1 without >> fully qualified name, .i.e db1.t1 (assuming db1 is current database when >> this temporary table is created). >> >> Only #2 and #3 followed this behavior and I would vote for this since this >> makes such behavior consistent through temporal tables and functions. >> >> Why I'm not voting for #3 is a special catalog and database just looks very >> hacky to me. It gave a imply that our built-in functions saved at a >> special >> catalog and database, which is actually not. Introducing a dedicated >> keyword >> like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and >> straightforward. One can argue that we should avoid introducing new >> keyword, >> but it's also very rare that a system can overwrite built-in functions. >> Since we >> decided to support this, introduce a new keyword is not a big deal IMO. >> >> Best, >> Kurt >> >> >> On Thu, Sep 19, 2019 at 3:07 PM Piotr Nowojski >> wrote: >> >>> Hi, >>> >>> It is a quite long discussion to follow and I hope I didn’t misunderstand >>> anything. From the proposals presented by Xuefu I would vote: >>> >>> -1 for #1 and #2 >>> +1 for #3 >>> >>> Besides #3 being IMO more general and more consistent, having qualified >>> names (#3) would help/make easier for someone to use cross >>> databases/catalogs queries (joining multiple data sets/streams). For >>> example with some functions to manipulate/clean up/convert the stored data >>> in different catalogs registered in the respective catalogs. >>> >>> Piotrek >>> On 19 Sep 2019, at 06:35, Jark Wu wrote: I agree with Xuefu that inconsistent handling with all the other >>> objects is not a big problem. Regarding to option#3, the special "system.system" namespace may confuse users. Users need to know the set of built-in function names to know when to >>> use "system.system" namespace. What will happen if user registers a non-builtin function name under the "system.system" namespace? Besides, I think it doesn't solve the "explode" problem I mentioned at >>> the beginning of this thread. So here is my vote: +1 for #1 0 for #2 -1 for #3 Best, Jark On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: > @Dawid, Re: we also don't need additional referencing the >>> specialcatalog > anywhere. > > True. But once we allow such reference, then user can do so in any >>> possible > place where a function name is expected, for which we have to handle. > That's a big difference, I think. > > Thanks, > Xuefu > > On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < > wysakowicz.da...@gmail.com> > wrote: > >> @Bowen I am not suggesting introducing additional catalog. I think we > need >> to get rid of the current built-in catalog.
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
I know Hive and Spark can shadow built-in functions by temporary function. Mysql, Oracle, Sql server can not shadow. User can use full names to access functions instead of shadowing. So I think it is a completely new thing, and the direct way to deal with new things is to add new grammar. So, +1 for #2, +0 for #3, -1 for #1 Best, Jingsong Lee -- From:Kurt Young Send Time:2019年9月19日(星期四) 16:43 To:dev Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog And let me make my vote complete: -1 for #1 +1 for #2 with different keyword -0 for #3 Best, Kurt On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > Looks like I'm the only person who is willing to +1 to #2 for now :-) > But I would suggest to change the keyword from GLOBAL to > something like BUILTIN. > > I think #2 and #3 are almost the same proposal, just with different > format to indicate whether it want to override built-in functions. > > My biggest reason to choose it is I want this behavior be consistent > with temporal tables. I will give some examples to show the behavior > and also make sure I'm not misunderstanding anything here. > > For most DBs, when user create a temporary table with: > > CREATE TEMPORARY TABLE t1 > > It's actually equivalent with: > > CREATE TEMPORARY TABLE `curent_db`.t1 > > If user change current database, they will not be able to access t1 without > fully qualified name, .i.e db1.t1 (assuming db1 is current database when > this temporary table is created). > > Only #2 and #3 followed this behavior and I would vote for this since this > makes such behavior consistent through temporal tables and functions. > > Why I'm not voting for #3 is a special catalog and database just looks very > hacky to me. It gave a imply that our built-in functions saved at a > special > catalog and database, which is actually not. Introducing a dedicated > keyword > like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and > straightforward. One can argue that we should avoid introducing new > keyword, > but it's also very rare that a system can overwrite built-in functions. > Since we > decided to support this, introduce a new keyword is not a big deal IMO. > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 3:07 PM Piotr Nowojski > wrote: > >> Hi, >> >> It is a quite long discussion to follow and I hope I didn’t misunderstand >> anything. From the proposals presented by Xuefu I would vote: >> >> -1 for #1 and #2 >> +1 for #3 >> >> Besides #3 being IMO more general and more consistent, having qualified >> names (#3) would help/make easier for someone to use cross >> databases/catalogs queries (joining multiple data sets/streams). For >> example with some functions to manipulate/clean up/convert the stored data >> in different catalogs registered in the respective catalogs. >> >> Piotrek >> >> > On 19 Sep 2019, at 06:35, Jark Wu wrote: >> > >> > I agree with Xuefu that inconsistent handling with all the other >> objects is >> > not a big problem. >> > >> > Regarding to option#3, the special "system.system" namespace may confuse >> > users. >> > Users need to know the set of built-in function names to know when to >> use >> > "system.system" namespace. >> > What will happen if user registers a non-builtin function name under the >> > "system.system" namespace? >> > Besides, I think it doesn't solve the "explode" problem I mentioned at >> the >> > beginning of this thread. >> > >> > So here is my vote: >> > >> > +1 for #1 >> > 0 for #2 >> > -1 for #3 >> > >> > Best, >> > Jark >> > >> > >> > On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: >> > >> >> @Dawid, Re: we also don't need additional referencing the >> specialcatalog >> >> anywhere. >> >> >> >> True. But once we allow such reference, then user can do so in any >> possible >> >> place where a function name is expected, for which we have to handle. >> >> That's a big difference, I think. >> >> >> >> Thanks, >> >> Xuefu >> >> >> >> On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < >> >> wysakowicz.da...@gmail.com> >> >> wrote: >> >> >> >>> @Bowen I am not suggesting introducing additional catalog. I think we >> >> need >> >>> to get rid of the current built-in catalog. >> >>> >> >>> @Xuefu in option #3 we also don't need additional referencing the >> special >> >>> catalog anywhere else besides in the CREATE statement. The resolution >> >>> behaviour is exactly the same in both options. >> >>> >> >>> On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: >> >>> >> Hi Dawid, >> >> "GLOBAL" is a temporary keyword that was given to the approach. It >> can >> >> be >> changed to something else for better. >> >> The difference between this and the #3 approach is that we only need >> >> the >> keyword for this create DDL. For other places (such as function >> referencing), no keyword or special namespace is needed. >> >> Thanks, >> Xuefu >> >> On Wed, Sep 18, 2019 at
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
And let me make my vote complete: -1 for #1 +1 for #2 with different keyword -0 for #3 Best, Kurt On Thu, Sep 19, 2019 at 4:40 PM Kurt Young wrote: > Looks like I'm the only person who is willing to +1 to #2 for now :-) > But I would suggest to change the keyword from GLOBAL to > something like BUILTIN. > > I think #2 and #3 are almost the same proposal, just with different > format to indicate whether it want to override built-in functions. > > My biggest reason to choose it is I want this behavior be consistent > with temporal tables. I will give some examples to show the behavior > and also make sure I'm not misunderstanding anything here. > > For most DBs, when user create a temporary table with: > > CREATE TEMPORARY TABLE t1 > > It's actually equivalent with: > > CREATE TEMPORARY TABLE `curent_db`.t1 > > If user change current database, they will not be able to access t1 without > fully qualified name, .i.e db1.t1 (assuming db1 is current database when > this temporary table is created). > > Only #2 and #3 followed this behavior and I would vote for this since this > makes such behavior consistent through temporal tables and functions. > > Why I'm not voting for #3 is a special catalog and database just looks very > hacky to me. It gave a imply that our built-in functions saved at a > special > catalog and database, which is actually not. Introducing a dedicated > keyword > like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and > straightforward. One can argue that we should avoid introducing new > keyword, > but it's also very rare that a system can overwrite built-in functions. > Since we > decided to support this, introduce a new keyword is not a big deal IMO. > > Best, > Kurt > > > On Thu, Sep 19, 2019 at 3:07 PM Piotr Nowojski > wrote: > >> Hi, >> >> It is a quite long discussion to follow and I hope I didn’t misunderstand >> anything. From the proposals presented by Xuefu I would vote: >> >> -1 for #1 and #2 >> +1 for #3 >> >> Besides #3 being IMO more general and more consistent, having qualified >> names (#3) would help/make easier for someone to use cross >> databases/catalogs queries (joining multiple data sets/streams). For >> example with some functions to manipulate/clean up/convert the stored data >> in different catalogs registered in the respective catalogs. >> >> Piotrek >> >> > On 19 Sep 2019, at 06:35, Jark Wu wrote: >> > >> > I agree with Xuefu that inconsistent handling with all the other >> objects is >> > not a big problem. >> > >> > Regarding to option#3, the special "system.system" namespace may confuse >> > users. >> > Users need to know the set of built-in function names to know when to >> use >> > "system.system" namespace. >> > What will happen if user registers a non-builtin function name under the >> > "system.system" namespace? >> > Besides, I think it doesn't solve the "explode" problem I mentioned at >> the >> > beginning of this thread. >> > >> > So here is my vote: >> > >> > +1 for #1 >> > 0 for #2 >> > -1 for #3 >> > >> > Best, >> > Jark >> > >> > >> > On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: >> > >> >> @Dawid, Re: we also don't need additional referencing the >> specialcatalog >> >> anywhere. >> >> >> >> True. But once we allow such reference, then user can do so in any >> possible >> >> place where a function name is expected, for which we have to handle. >> >> That's a big difference, I think. >> >> >> >> Thanks, >> >> Xuefu >> >> >> >> On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < >> >> wysakowicz.da...@gmail.com> >> >> wrote: >> >> >> >>> @Bowen I am not suggesting introducing additional catalog. I think we >> >> need >> >>> to get rid of the current built-in catalog. >> >>> >> >>> @Xuefu in option #3 we also don't need additional referencing the >> special >> >>> catalog anywhere else besides in the CREATE statement. The resolution >> >>> behaviour is exactly the same in both options. >> >>> >> >>> On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: >> >>> >> Hi Dawid, >> >> "GLOBAL" is a temporary keyword that was given to the approach. It >> can >> >> be >> changed to something else for better. >> >> The difference between this and the #3 approach is that we only need >> >> the >> keyword for this create DDL. For other places (such as function >> referencing), no keyword or special namespace is needed. >> >> Thanks, >> Xuefu >> >> On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < >> wysakowicz.da...@gmail.com> >> wrote: >> >> > Hi, >> > I think it makes sense to start voting at this point. >> > >> > Option 1: Only 1-part identifiers >> > PROS: >> > - allows shadowing built-in functions >> > CONS: >> > - incosistent with all the other objects, both permanent & temporary >> > - does not allow shadowing catalog functions >> > >> > Option 2: Special keyword for built-in function >> > I think this is quite similar to
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Looks like I'm the only person who is willing to +1 to #2 for now :-) But I would suggest to change the keyword from GLOBAL to something like BUILTIN. I think #2 and #3 are almost the same proposal, just with different format to indicate whether it want to override built-in functions. My biggest reason to choose it is I want this behavior be consistent with temporal tables. I will give some examples to show the behavior and also make sure I'm not misunderstanding anything here. For most DBs, when user create a temporary table with: CREATE TEMPORARY TABLE t1 It's actually equivalent with: CREATE TEMPORARY TABLE `curent_db`.t1 If user change current database, they will not be able to access t1 without fully qualified name, .i.e db1.t1 (assuming db1 is current database when this temporary table is created). Only #2 and #3 followed this behavior and I would vote for this since this makes such behavior consistent through temporal tables and functions. Why I'm not voting for #3 is a special catalog and database just looks very hacky to me. It gave a imply that our built-in functions saved at a special catalog and database, which is actually not. Introducing a dedicated keyword like CREATE TEMPORARY BUILTIN FUNCTION looks more clear and straightforward. One can argue that we should avoid introducing new keyword, but it's also very rare that a system can overwrite built-in functions. Since we decided to support this, introduce a new keyword is not a big deal IMO. Best, Kurt On Thu, Sep 19, 2019 at 3:07 PM Piotr Nowojski wrote: > Hi, > > It is a quite long discussion to follow and I hope I didn’t misunderstand > anything. From the proposals presented by Xuefu I would vote: > > -1 for #1 and #2 > +1 for #3 > > Besides #3 being IMO more general and more consistent, having qualified > names (#3) would help/make easier for someone to use cross > databases/catalogs queries (joining multiple data sets/streams). For > example with some functions to manipulate/clean up/convert the stored data > in different catalogs registered in the respective catalogs. > > Piotrek > > > On 19 Sep 2019, at 06:35, Jark Wu wrote: > > > > I agree with Xuefu that inconsistent handling with all the other objects > is > > not a big problem. > > > > Regarding to option#3, the special "system.system" namespace may confuse > > users. > > Users need to know the set of built-in function names to know when to use > > "system.system" namespace. > > What will happen if user registers a non-builtin function name under the > > "system.system" namespace? > > Besides, I think it doesn't solve the "explode" problem I mentioned at > the > > beginning of this thread. > > > > So here is my vote: > > > > +1 for #1 > > 0 for #2 > > -1 for #3 > > > > Best, > > Jark > > > > > > On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: > > > >> @Dawid, Re: we also don't need additional referencing the specialcatalog > >> anywhere. > >> > >> True. But once we allow such reference, then user can do so in any > possible > >> place where a function name is expected, for which we have to handle. > >> That's a big difference, I think. > >> > >> Thanks, > >> Xuefu > >> > >> On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < > >> wysakowicz.da...@gmail.com> > >> wrote: > >> > >>> @Bowen I am not suggesting introducing additional catalog. I think we > >> need > >>> to get rid of the current built-in catalog. > >>> > >>> @Xuefu in option #3 we also don't need additional referencing the > special > >>> catalog anywhere else besides in the CREATE statement. The resolution > >>> behaviour is exactly the same in both options. > >>> > >>> On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: > >>> > Hi Dawid, > > "GLOBAL" is a temporary keyword that was given to the approach. It can > >> be > changed to something else for better. > > The difference between this and the #3 approach is that we only need > >> the > keyword for this create DDL. For other places (such as function > referencing), no keyword or special namespace is needed. > > Thanks, > Xuefu > > On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < > wysakowicz.da...@gmail.com> > wrote: > > > Hi, > > I think it makes sense to start voting at this point. > > > > Option 1: Only 1-part identifiers > > PROS: > > - allows shadowing built-in functions > > CONS: > > - incosistent with all the other objects, both permanent & temporary > > - does not allow shadowing catalog functions > > > > Option 2: Special keyword for built-in function > > I think this is quite similar to the special catalog/db. The thing I > >> am > > strongly against in this proposal is the GLOBAL keyword. This keyword > has a > > meaning in rdbms systems and means a function that is present for a > > lifetime of a session in which it was created, but available in all > >>> other > > sessions. Therefore I really don't
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, It is a quite long discussion to follow and I hope I didn’t misunderstand anything. From the proposals presented by Xuefu I would vote: -1 for #1 and #2 +1 for #3 Besides #3 being IMO more general and more consistent, having qualified names (#3) would help/make easier for someone to use cross databases/catalogs queries (joining multiple data sets/streams). For example with some functions to manipulate/clean up/convert the stored data in different catalogs registered in the respective catalogs. Piotrek > On 19 Sep 2019, at 06:35, Jark Wu wrote: > > I agree with Xuefu that inconsistent handling with all the other objects is > not a big problem. > > Regarding to option#3, the special "system.system" namespace may confuse > users. > Users need to know the set of built-in function names to know when to use > "system.system" namespace. > What will happen if user registers a non-builtin function name under the > "system.system" namespace? > Besides, I think it doesn't solve the "explode" problem I mentioned at the > beginning of this thread. > > So here is my vote: > > +1 for #1 > 0 for #2 > -1 for #3 > > Best, > Jark > > > On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: > >> @Dawid, Re: we also don't need additional referencing the specialcatalog >> anywhere. >> >> True. But once we allow such reference, then user can do so in any possible >> place where a function name is expected, for which we have to handle. >> That's a big difference, I think. >> >> Thanks, >> Xuefu >> >> On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < >> wysakowicz.da...@gmail.com> >> wrote: >> >>> @Bowen I am not suggesting introducing additional catalog. I think we >> need >>> to get rid of the current built-in catalog. >>> >>> @Xuefu in option #3 we also don't need additional referencing the special >>> catalog anywhere else besides in the CREATE statement. The resolution >>> behaviour is exactly the same in both options. >>> >>> On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: >>> Hi Dawid, "GLOBAL" is a temporary keyword that was given to the approach. It can >> be changed to something else for better. The difference between this and the #3 approach is that we only need >> the keyword for this create DDL. For other places (such as function referencing), no keyword or special namespace is needed. Thanks, Xuefu On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < wysakowicz.da...@gmail.com> wrote: > Hi, > I think it makes sense to start voting at this point. > > Option 1: Only 1-part identifiers > PROS: > - allows shadowing built-in functions > CONS: > - incosistent with all the other objects, both permanent & temporary > - does not allow shadowing catalog functions > > Option 2: Special keyword for built-in function > I think this is quite similar to the special catalog/db. The thing I >> am > strongly against in this proposal is the GLOBAL keyword. This keyword has a > meaning in rdbms systems and means a function that is present for a > lifetime of a session in which it was created, but available in all >>> other > sessions. Therefore I really don't want to use this keyword in a different > context. > > Option 3: Special catalog/db > > PROS: > - allows shadowing built-in functions > - allows shadowing catalog functions > - consistent with other objects > CONS: > - we introduce a special namespace for built-in functions > > I don't see a problem with introducing the special namespace. In the >>> end it > is very similar to the keyword approach. In this case the catalog/db > combination would be the "keyword" > > Therefore my votes: > Option 1: -0 > Option 2: -1 (I might change to +0 if we can come up with a better keyword) > Option 3: +1 > > Best, > Dawid > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > >> Hi Aljoscha, >> >> Thanks for the summary and these are great questions to be >> answered. The >> answer to your first question is clear: there is a general >> agreement >>> to >> override built-in functions with temp functions. >> >> However, your second and third questions are sort of related, as a > function >> reference can be either just function name (like "func") or in the >>> form > or >> "cat.db.func". When a reference is just function name, it can mean > either a >> built-in function or a function defined in the current cat/db. If >> we >> support overriding a built-in function with a temp function, such >> overriding can also cover a function in the current cat/db. >> >> I think what Timo referred as "overriding a catalog function" >> means a > temp >> function defined as "cat.db.func" overrides a catalog function >> "func" in
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
I agree with Xuefu that inconsistent handling with all the other objects is not a big problem. Regarding to option#3, the special "system.system" namespace may confuse users. Users need to know the set of built-in function names to know when to use "system.system" namespace. What will happen if user registers a non-builtin function name under the "system.system" namespace? Besides, I think it doesn't solve the "explode" problem I mentioned at the beginning of this thread. So here is my vote: +1 for #1 0 for #2 -1 for #3 Best, Jark On Thu, 19 Sep 2019 at 08:38, Xuefu Z wrote: > @Dawid, Re: we also don't need additional referencing the specialcatalog > anywhere. > > True. But once we allow such reference, then user can do so in any possible > place where a function name is expected, for which we have to handle. > That's a big difference, I think. > > Thanks, > Xuefu > > On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz < > wysakowicz.da...@gmail.com> > wrote: > > > @Bowen I am not suggesting introducing additional catalog. I think we > need > > to get rid of the current built-in catalog. > > > > @Xuefu in option #3 we also don't need additional referencing the special > > catalog anywhere else besides in the CREATE statement. The resolution > > behaviour is exactly the same in both options. > > > > On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: > > > > > Hi Dawid, > > > > > > "GLOBAL" is a temporary keyword that was given to the approach. It can > be > > > changed to something else for better. > > > > > > The difference between this and the #3 approach is that we only need > the > > > keyword for this create DDL. For other places (such as function > > > referencing), no keyword or special namespace is needed. > > > > > > Thanks, > > > Xuefu > > > > > > On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < > > > wysakowicz.da...@gmail.com> > > > wrote: > > > > > > > Hi, > > > > I think it makes sense to start voting at this point. > > > > > > > > Option 1: Only 1-part identifiers > > > > PROS: > > > > - allows shadowing built-in functions > > > > CONS: > > > > - incosistent with all the other objects, both permanent & temporary > > > > - does not allow shadowing catalog functions > > > > > > > > Option 2: Special keyword for built-in function > > > > I think this is quite similar to the special catalog/db. The thing I > am > > > > strongly against in this proposal is the GLOBAL keyword. This keyword > > > has a > > > > meaning in rdbms systems and means a function that is present for a > > > > lifetime of a session in which it was created, but available in all > > other > > > > sessions. Therefore I really don't want to use this keyword in a > > > different > > > > context. > > > > > > > > Option 3: Special catalog/db > > > > > > > > PROS: > > > > - allows shadowing built-in functions > > > > - allows shadowing catalog functions > > > > - consistent with other objects > > > > CONS: > > > > - we introduce a special namespace for built-in functions > > > > > > > > I don't see a problem with introducing the special namespace. In the > > end > > > it > > > > is very similar to the keyword approach. In this case the catalog/db > > > > combination would be the "keyword" > > > > > > > > Therefore my votes: > > > > Option 1: -0 > > > > Option 2: -1 (I might change to +0 if we can come up with a better > > > keyword) > > > > Option 3: +1 > > > > > > > > Best, > > > > Dawid > > > > > > > > > > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > > > > > > > Hi Aljoscha, > > > > > > > > > > Thanks for the summary and these are great questions to be > answered. > > > The > > > > > answer to your first question is clear: there is a general > agreement > > to > > > > > override built-in functions with temp functions. > > > > > > > > > > However, your second and third questions are sort of related, as a > > > > function > > > > > reference can be either just function name (like "func") or in the > > form > > > > or > > > > > "cat.db.func". When a reference is just function name, it can mean > > > > either a > > > > > built-in function or a function defined in the current cat/db. If > we > > > > > support overriding a built-in function with a temp function, such > > > > > overriding can also cover a function in the current cat/db. > > > > > > > > > > I think what Timo referred as "overriding a catalog function" > means a > > > > temp > > > > > function defined as "cat.db.func" overrides a catalog function > "func" > > > in > > > > > cat/db even if cat/db is not current. To support this, temp > function > > > has > > > > to > > > > > be tied to a cat/db. What's why I said above that the 2nd and 3rd > > > > questions > > > > > are related. The problem with such support is the ambiguity when > user > > > > > defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func > > ...". > > > > > Here "func" can means a global temp function, or a temp function in > > > > current > > > > > cat/db. If we can assume the former,
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
@Dawid, Re: we also don't need additional referencing the specialcatalog anywhere. True. But once we allow such reference, then user can do so in any possible place where a function name is expected, for which we have to handle. That's a big difference, I think. Thanks, Xuefu On Wed, Sep 18, 2019 at 5:25 PM Dawid Wysakowicz wrote: > @Bowen I am not suggesting introducing additional catalog. I think we need > to get rid of the current built-in catalog. > > @Xuefu in option #3 we also don't need additional referencing the special > catalog anywhere else besides in the CREATE statement. The resolution > behaviour is exactly the same in both options. > > On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: > > > Hi Dawid, > > > > "GLOBAL" is a temporary keyword that was given to the approach. It can be > > changed to something else for better. > > > > The difference between this and the #3 approach is that we only need the > > keyword for this create DDL. For other places (such as function > > referencing), no keyword or special namespace is needed. > > > > Thanks, > > Xuefu > > > > On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < > > wysakowicz.da...@gmail.com> > > wrote: > > > > > Hi, > > > I think it makes sense to start voting at this point. > > > > > > Option 1: Only 1-part identifiers > > > PROS: > > > - allows shadowing built-in functions > > > CONS: > > > - incosistent with all the other objects, both permanent & temporary > > > - does not allow shadowing catalog functions > > > > > > Option 2: Special keyword for built-in function > > > I think this is quite similar to the special catalog/db. The thing I am > > > strongly against in this proposal is the GLOBAL keyword. This keyword > > has a > > > meaning in rdbms systems and means a function that is present for a > > > lifetime of a session in which it was created, but available in all > other > > > sessions. Therefore I really don't want to use this keyword in a > > different > > > context. > > > > > > Option 3: Special catalog/db > > > > > > PROS: > > > - allows shadowing built-in functions > > > - allows shadowing catalog functions > > > - consistent with other objects > > > CONS: > > > - we introduce a special namespace for built-in functions > > > > > > I don't see a problem with introducing the special namespace. In the > end > > it > > > is very similar to the keyword approach. In this case the catalog/db > > > combination would be the "keyword" > > > > > > Therefore my votes: > > > Option 1: -0 > > > Option 2: -1 (I might change to +0 if we can come up with a better > > keyword) > > > Option 3: +1 > > > > > > Best, > > > Dawid > > > > > > > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > > > > > Hi Aljoscha, > > > > > > > > Thanks for the summary and these are great questions to be answered. > > The > > > > answer to your first question is clear: there is a general agreement > to > > > > override built-in functions with temp functions. > > > > > > > > However, your second and third questions are sort of related, as a > > > function > > > > reference can be either just function name (like "func") or in the > form > > > or > > > > "cat.db.func". When a reference is just function name, it can mean > > > either a > > > > built-in function or a function defined in the current cat/db. If we > > > > support overriding a built-in function with a temp function, such > > > > overriding can also cover a function in the current cat/db. > > > > > > > > I think what Timo referred as "overriding a catalog function" means a > > > temp > > > > function defined as "cat.db.func" overrides a catalog function "func" > > in > > > > cat/db even if cat/db is not current. To support this, temp function > > has > > > to > > > > be tied to a cat/db. What's why I said above that the 2nd and 3rd > > > questions > > > > are related. The problem with such support is the ambiguity when user > > > > defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func > ...". > > > > Here "func" can means a global temp function, or a temp function in > > > current > > > > cat/db. If we can assume the former, this creates an inconsistency > > > because > > > > "CREATE FUNCTION func" actually means a function in current cat/db. > If > > we > > > > assume the latter, then there is no way for user to create a global > > temp > > > > function. > > > > > > > > Giving a special namespace for built-in functions may solve the > > ambiguity > > > > problem above, but it also introduces artificial catalog/database > that > > > > needs special treatment and pollutes the cleanness of the code. I > > would > > > > rather introduce a syntax in DDL to solve the problem, like "CREATE > > > > [GLOBAL] TEMPORARY FUNCTION func". > > > > > > > > Thus, I'd like to summarize a few candidate proposals for voting > > > purposes: > > > > > > > > 1. Support only global, temporary functions without namespace. Such > > temp > > > > functions overrides built-in functions and catalog functions in >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Re: The reason why I prefer option 3 is that in option 3 all objects internally are identified with 3 parts. True, but the problem we have is not about how to differentiate each type objects internally. Rather, it's rather about how a user referencing an object unambiguously and consistently. Thanks, Xuefu On Wed, Sep 18, 2019 at 4:55 PM Dawid Wysakowicz wrote: > Last additional comment on Option 2. The reason why I prefer option 3 is > that in option 3 all objects internally are identified with 3 parts. This > makes it easier to handle at different locations e.g. while persisting > views, as all objects have uniform representation. > > On Thu, 19 Sep 2019, 07:31 Dawid Wysakowicz, > wrote: > > > Hi, > > I think it makes sense to start voting at this point. > > > > Option 1: Only 1-part identifiers > > PROS: > > - allows shadowing built-in functions > > CONS: > > - incosistent with all the other objects, both permanent & temporary > > - does not allow shadowing catalog functions > > > > Option 2: Special keyword for built-in function > > I think this is quite similar to the special catalog/db. The thing I am > > strongly against in this proposal is the GLOBAL keyword. This keyword > has a > > meaning in rdbms systems and means a function that is present for a > > lifetime of a session in which it was created, but available in all other > > sessions. Therefore I really don't want to use this keyword in a > different > > context. > > > > Option 3: Special catalog/db > > > > PROS: > > - allows shadowing built-in functions > > - allows shadowing catalog functions > > - consistent with other objects > > CONS: > > - we introduce a special namespace for built-in functions > > > > I don't see a problem with introducing the special namespace. In the end > > it is very similar to the keyword approach. In this case the catalog/db > > combination would be the "keyword" > > > > Therefore my votes: > > Option 1: -0 > > Option 2: -1 (I might change to +0 if we can come up with a better > keyword) > > Option 3: +1 > > > > Best, > > Dawid > > > > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > >> Hi Aljoscha, > >> > >> Thanks for the summary and these are great questions to be answered. The > >> answer to your first question is clear: there is a general agreement to > >> override built-in functions with temp functions. > >> > >> However, your second and third questions are sort of related, as a > >> function > >> reference can be either just function name (like "func") or in the form > or > >> "cat.db.func". When a reference is just function name, it can mean > either > >> a > >> built-in function or a function defined in the current cat/db. If we > >> support overriding a built-in function with a temp function, such > >> overriding can also cover a function in the current cat/db. > >> > >> I think what Timo referred as "overriding a catalog function" means a > temp > >> function defined as "cat.db.func" overrides a catalog function "func" in > >> cat/db even if cat/db is not current. To support this, temp function has > >> to > >> be tied to a cat/db. What's why I said above that the 2nd and 3rd > >> questions > >> are related. The problem with such support is the ambiguity when user > >> defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". > >> Here "func" can means a global temp function, or a temp function in > >> current > >> cat/db. If we can assume the former, this creates an inconsistency > because > >> "CREATE FUNCTION func" actually means a function in current cat/db. If > we > >> assume the latter, then there is no way for user to create a global temp > >> function. > >> > >> Giving a special namespace for built-in functions may solve the > ambiguity > >> problem above, but it also introduces artificial catalog/database that > >> needs special treatment and pollutes the cleanness of the code. I would > >> rather introduce a syntax in DDL to solve the problem, like "CREATE > >> [GLOBAL] TEMPORARY FUNCTION func". > >> > >> Thus, I'd like to summarize a few candidate proposals for voting > purposes: > >> > >> 1. Support only global, temporary functions without namespace. Such temp > >> functions overrides built-in functions and catalog functions in current > >> cat/db. The resolution order is: temp functions -> built-in functions -> > >> catalog functions. (Partially or fully qualified functions has no > >> ambiguity!) > >> > >> 2. In addition to #1, support creating and referencing temporary > functions > >> associated with a cat/db with "GLOBAL" qualifier in DDL for global temp > >> functions. The resolution order is: global temp functions -> built-in > >> functions -> temp functions in current cat/db -> catalog function. > >> (Resolution for partially or fully qualified function reference is: temp > >> functions -> persistent functions.) > >> > >> 3. In addition to #1, support creating and referencing temporary > functions > >> associated with a cat/db with a special namespace for
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
@Bowen I am not suggesting introducing additional catalog. I think we need to get rid of the current built-in catalog. @Xuefu in option #3 we also don't need additional referencing the special catalog anywhere else besides in the CREATE statement. The resolution behaviour is exactly the same in both options. On Thu, 19 Sep 2019, 08:17 Xuefu Z, wrote: > Hi Dawid, > > "GLOBAL" is a temporary keyword that was given to the approach. It can be > changed to something else for better. > > The difference between this and the #3 approach is that we only need the > keyword for this create DDL. For other places (such as function > referencing), no keyword or special namespace is needed. > > Thanks, > Xuefu > > On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz < > wysakowicz.da...@gmail.com> > wrote: > > > Hi, > > I think it makes sense to start voting at this point. > > > > Option 1: Only 1-part identifiers > > PROS: > > - allows shadowing built-in functions > > CONS: > > - incosistent with all the other objects, both permanent & temporary > > - does not allow shadowing catalog functions > > > > Option 2: Special keyword for built-in function > > I think this is quite similar to the special catalog/db. The thing I am > > strongly against in this proposal is the GLOBAL keyword. This keyword > has a > > meaning in rdbms systems and means a function that is present for a > > lifetime of a session in which it was created, but available in all other > > sessions. Therefore I really don't want to use this keyword in a > different > > context. > > > > Option 3: Special catalog/db > > > > PROS: > > - allows shadowing built-in functions > > - allows shadowing catalog functions > > - consistent with other objects > > CONS: > > - we introduce a special namespace for built-in functions > > > > I don't see a problem with introducing the special namespace. In the end > it > > is very similar to the keyword approach. In this case the catalog/db > > combination would be the "keyword" > > > > Therefore my votes: > > Option 1: -0 > > Option 2: -1 (I might change to +0 if we can come up with a better > keyword) > > Option 3: +1 > > > > Best, > > Dawid > > > > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > > > Hi Aljoscha, > > > > > > Thanks for the summary and these are great questions to be answered. > The > > > answer to your first question is clear: there is a general agreement to > > > override built-in functions with temp functions. > > > > > > However, your second and third questions are sort of related, as a > > function > > > reference can be either just function name (like "func") or in the form > > or > > > "cat.db.func". When a reference is just function name, it can mean > > either a > > > built-in function or a function defined in the current cat/db. If we > > > support overriding a built-in function with a temp function, such > > > overriding can also cover a function in the current cat/db. > > > > > > I think what Timo referred as "overriding a catalog function" means a > > temp > > > function defined as "cat.db.func" overrides a catalog function "func" > in > > > cat/db even if cat/db is not current. To support this, temp function > has > > to > > > be tied to a cat/db. What's why I said above that the 2nd and 3rd > > questions > > > are related. The problem with such support is the ambiguity when user > > > defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". > > > Here "func" can means a global temp function, or a temp function in > > current > > > cat/db. If we can assume the former, this creates an inconsistency > > because > > > "CREATE FUNCTION func" actually means a function in current cat/db. If > we > > > assume the latter, then there is no way for user to create a global > temp > > > function. > > > > > > Giving a special namespace for built-in functions may solve the > ambiguity > > > problem above, but it also introduces artificial catalog/database that > > > needs special treatment and pollutes the cleanness of the code. I > would > > > rather introduce a syntax in DDL to solve the problem, like "CREATE > > > [GLOBAL] TEMPORARY FUNCTION func". > > > > > > Thus, I'd like to summarize a few candidate proposals for voting > > purposes: > > > > > > 1. Support only global, temporary functions without namespace. Such > temp > > > functions overrides built-in functions and catalog functions in current > > > cat/db. The resolution order is: temp functions -> built-in functions > -> > > > catalog functions. (Partially or fully qualified functions has no > > > ambiguity!) > > > > > > 2. In addition to #1, support creating and referencing temporary > > functions > > > associated with a cat/db with "GLOBAL" qualifier in DDL for global temp > > > functions. The resolution order is: global temp functions -> built-in > > > functions -> temp functions in current cat/db -> catalog function. > > > (Resolution for partially or fully qualified function reference is: > temp > > > functions ->
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Dawid, "GLOBAL" is a temporary keyword that was given to the approach. It can be changed to something else for better. The difference between this and the #3 approach is that we only need the keyword for this create DDL. For other places (such as function referencing), no keyword or special namespace is needed. Thanks, Xuefu On Wed, Sep 18, 2019 at 4:32 PM Dawid Wysakowicz wrote: > Hi, > I think it makes sense to start voting at this point. > > Option 1: Only 1-part identifiers > PROS: > - allows shadowing built-in functions > CONS: > - incosistent with all the other objects, both permanent & temporary > - does not allow shadowing catalog functions > > Option 2: Special keyword for built-in function > I think this is quite similar to the special catalog/db. The thing I am > strongly against in this proposal is the GLOBAL keyword. This keyword has a > meaning in rdbms systems and means a function that is present for a > lifetime of a session in which it was created, but available in all other > sessions. Therefore I really don't want to use this keyword in a different > context. > > Option 3: Special catalog/db > > PROS: > - allows shadowing built-in functions > - allows shadowing catalog functions > - consistent with other objects > CONS: > - we introduce a special namespace for built-in functions > > I don't see a problem with introducing the special namespace. In the end it > is very similar to the keyword approach. In this case the catalog/db > combination would be the "keyword" > > Therefore my votes: > Option 1: -0 > Option 2: -1 (I might change to +0 if we can come up with a better keyword) > Option 3: +1 > > Best, > Dawid > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > Hi Aljoscha, > > > > Thanks for the summary and these are great questions to be answered. The > > answer to your first question is clear: there is a general agreement to > > override built-in functions with temp functions. > > > > However, your second and third questions are sort of related, as a > function > > reference can be either just function name (like "func") or in the form > or > > "cat.db.func". When a reference is just function name, it can mean > either a > > built-in function or a function defined in the current cat/db. If we > > support overriding a built-in function with a temp function, such > > overriding can also cover a function in the current cat/db. > > > > I think what Timo referred as "overriding a catalog function" means a > temp > > function defined as "cat.db.func" overrides a catalog function "func" in > > cat/db even if cat/db is not current. To support this, temp function has > to > > be tied to a cat/db. What's why I said above that the 2nd and 3rd > questions > > are related. The problem with such support is the ambiguity when user > > defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". > > Here "func" can means a global temp function, or a temp function in > current > > cat/db. If we can assume the former, this creates an inconsistency > because > > "CREATE FUNCTION func" actually means a function in current cat/db. If we > > assume the latter, then there is no way for user to create a global temp > > function. > > > > Giving a special namespace for built-in functions may solve the ambiguity > > problem above, but it also introduces artificial catalog/database that > > needs special treatment and pollutes the cleanness of the code. I would > > rather introduce a syntax in DDL to solve the problem, like "CREATE > > [GLOBAL] TEMPORARY FUNCTION func". > > > > Thus, I'd like to summarize a few candidate proposals for voting > purposes: > > > > 1. Support only global, temporary functions without namespace. Such temp > > functions overrides built-in functions and catalog functions in current > > cat/db. The resolution order is: temp functions -> built-in functions -> > > catalog functions. (Partially or fully qualified functions has no > > ambiguity!) > > > > 2. In addition to #1, support creating and referencing temporary > functions > > associated with a cat/db with "GLOBAL" qualifier in DDL for global temp > > functions. The resolution order is: global temp functions -> built-in > > functions -> temp functions in current cat/db -> catalog function. > > (Resolution for partially or fully qualified function reference is: temp > > functions -> persistent functions.) > > > > 3. In addition to #1, support creating and referencing temporary > functions > > associated with a cat/db with a special namespace for built-in functions > > and global temp functions. The resolution is the same as #2, except that > > the special namespace might be prefixed to a reference to a built-in > > function or global temp function. (In absence of the special namespace, > the > > resolution order is the same as in #2.) > > > > My personal preference is #1, given the unknown use case and introduced > > complexity for #2 and #3. However, #2 is an acceptable alternative. Thus, > > my votes are: >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, For #2, as Xuefu and I discussed offline, the key point is to introduce a keyword to SQL DDL to distinguish temp function that override built-in functions v.s. temp functions that override catalog functions. It can be something else than "GLOBAL", like "BUILTIN" (e.g. "CREATE BUILTIN TEMP FUNCTION") given there's no SQL standard for temp functions. This option is more about whether we want to have such a new keyword in SQL for the proposed functionality, and I personally think it's acceptable. For #3, besides the drawbacks mentioned by Xuefu and Jark, another con is: we already have a special catalog and db as "default_catalog" and "default_database", though they are not used very correctly at the moment (another story...), they are at least physically present. Introducing yet another virtual special catalog/db as something like "system"."system" that never physically exist would further confuse users, and hurt understandability and usability. Thus my vote is: +1 for #1 0 for #2 -1 for #3 Thanks, Bowen On Wed, Sep 18, 2019 at 4:55 PM Dawid Wysakowicz wrote: > Last additional comment on Option 2. The reason why I prefer option 3 is > that in option 3 all objects internally are identified with 3 parts. This > makes it easier to handle at different locations e.g. while persisting > views, as all objects have uniform representation. > > On Thu, 19 Sep 2019, 07:31 Dawid Wysakowicz, > wrote: > > > Hi, > > I think it makes sense to start voting at this point. > > > > Option 1: Only 1-part identifiers > > PROS: > > - allows shadowing built-in functions > > CONS: > > - incosistent with all the other objects, both permanent & temporary > > - does not allow shadowing catalog functions > > > > Option 2: Special keyword for built-in function > > I think this is quite similar to the special catalog/db. The thing I am > > strongly against in this proposal is the GLOBAL keyword. This keyword > has a > > meaning in rdbms systems and means a function that is present for a > > lifetime of a session in which it was created, but available in all other > > sessions. Therefore I really don't want to use this keyword in a > different > > context. > > > > Option 3: Special catalog/db > > > > PROS: > > - allows shadowing built-in functions > > - allows shadowing catalog functions > > - consistent with other objects > > CONS: > > - we introduce a special namespace for built-in functions > > > > I don't see a problem with introducing the special namespace. In the end > > it is very similar to the keyword approach. In this case the catalog/db > > combination would be the "keyword" > > > > Therefore my votes: > > Option 1: -0 > > Option 2: -1 (I might change to +0 if we can come up with a better > keyword) > > Option 3: +1 > > > > Best, > > Dawid > > > > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > > > >> Hi Aljoscha, > >> > >> Thanks for the summary and these are great questions to be answered. The > >> answer to your first question is clear: there is a general agreement to > >> override built-in functions with temp functions. > >> > >> However, your second and third questions are sort of related, as a > >> function > >> reference can be either just function name (like "func") or in the form > or > >> "cat.db.func". When a reference is just function name, it can mean > either > >> a > >> built-in function or a function defined in the current cat/db. If we > >> support overriding a built-in function with a temp function, such > >> overriding can also cover a function in the current cat/db. > >> > >> I think what Timo referred as "overriding a catalog function" means a > temp > >> function defined as "cat.db.func" overrides a catalog function "func" in > >> cat/db even if cat/db is not current. To support this, temp function has > >> to > >> be tied to a cat/db. What's why I said above that the 2nd and 3rd > >> questions > >> are related. The problem with such support is the ambiguity when user > >> defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". > >> Here "func" can means a global temp function, or a temp function in > >> current > >> cat/db. If we can assume the former, this creates an inconsistency > because > >> "CREATE FUNCTION func" actually means a function in current cat/db. If > we > >> assume the latter, then there is no way for user to create a global temp > >> function. > >> > >> Giving a special namespace for built-in functions may solve the > ambiguity > >> problem above, but it also introduces artificial catalog/database that > >> needs special treatment and pollutes the cleanness of the code. I would > >> rather introduce a syntax in DDL to solve the problem, like "CREATE > >> [GLOBAL] TEMPORARY FUNCTION func". > >> > >> Thus, I'd like to summarize a few candidate proposals for voting > purposes: > >> > >> 1. Support only global, temporary functions without namespace. Such temp > >> functions overrides built-in functions and catalog functions in current > >> cat/db. The
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Last additional comment on Option 2. The reason why I prefer option 3 is that in option 3 all objects internally are identified with 3 parts. This makes it easier to handle at different locations e.g. while persisting views, as all objects have uniform representation. On Thu, 19 Sep 2019, 07:31 Dawid Wysakowicz, wrote: > Hi, > I think it makes sense to start voting at this point. > > Option 1: Only 1-part identifiers > PROS: > - allows shadowing built-in functions > CONS: > - incosistent with all the other objects, both permanent & temporary > - does not allow shadowing catalog functions > > Option 2: Special keyword for built-in function > I think this is quite similar to the special catalog/db. The thing I am > strongly against in this proposal is the GLOBAL keyword. This keyword has a > meaning in rdbms systems and means a function that is present for a > lifetime of a session in which it was created, but available in all other > sessions. Therefore I really don't want to use this keyword in a different > context. > > Option 3: Special catalog/db > > PROS: > - allows shadowing built-in functions > - allows shadowing catalog functions > - consistent with other objects > CONS: > - we introduce a special namespace for built-in functions > > I don't see a problem with introducing the special namespace. In the end > it is very similar to the keyword approach. In this case the catalog/db > combination would be the "keyword" > > Therefore my votes: > Option 1: -0 > Option 2: -1 (I might change to +0 if we can come up with a better keyword) > Option 3: +1 > > Best, > Dawid > > > On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > >> Hi Aljoscha, >> >> Thanks for the summary and these are great questions to be answered. The >> answer to your first question is clear: there is a general agreement to >> override built-in functions with temp functions. >> >> However, your second and third questions are sort of related, as a >> function >> reference can be either just function name (like "func") or in the form or >> "cat.db.func". When a reference is just function name, it can mean either >> a >> built-in function or a function defined in the current cat/db. If we >> support overriding a built-in function with a temp function, such >> overriding can also cover a function in the current cat/db. >> >> I think what Timo referred as "overriding a catalog function" means a temp >> function defined as "cat.db.func" overrides a catalog function "func" in >> cat/db even if cat/db is not current. To support this, temp function has >> to >> be tied to a cat/db. What's why I said above that the 2nd and 3rd >> questions >> are related. The problem with such support is the ambiguity when user >> defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". >> Here "func" can means a global temp function, or a temp function in >> current >> cat/db. If we can assume the former, this creates an inconsistency because >> "CREATE FUNCTION func" actually means a function in current cat/db. If we >> assume the latter, then there is no way for user to create a global temp >> function. >> >> Giving a special namespace for built-in functions may solve the ambiguity >> problem above, but it also introduces artificial catalog/database that >> needs special treatment and pollutes the cleanness of the code. I would >> rather introduce a syntax in DDL to solve the problem, like "CREATE >> [GLOBAL] TEMPORARY FUNCTION func". >> >> Thus, I'd like to summarize a few candidate proposals for voting purposes: >> >> 1. Support only global, temporary functions without namespace. Such temp >> functions overrides built-in functions and catalog functions in current >> cat/db. The resolution order is: temp functions -> built-in functions -> >> catalog functions. (Partially or fully qualified functions has no >> ambiguity!) >> >> 2. In addition to #1, support creating and referencing temporary functions >> associated with a cat/db with "GLOBAL" qualifier in DDL for global temp >> functions. The resolution order is: global temp functions -> built-in >> functions -> temp functions in current cat/db -> catalog function. >> (Resolution for partially or fully qualified function reference is: temp >> functions -> persistent functions.) >> >> 3. In addition to #1, support creating and referencing temporary functions >> associated with a cat/db with a special namespace for built-in functions >> and global temp functions. The resolution is the same as #2, except that >> the special namespace might be prefixed to a reference to a built-in >> function or global temp function. (In absence of the special namespace, >> the >> resolution order is the same as in #2.) >> >> My personal preference is #1, given the unknown use case and introduced >> complexity for #2 and #3. However, #2 is an acceptable alternative. Thus, >> my votes are: >> >> +1 for #1 >> +0 for #2 >> -1 for #3 >> >> Everyone, please cast your vote (in above format please!), or let me know >> if you
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, I think it makes sense to start voting at this point. Option 1: Only 1-part identifiers PROS: - allows shadowing built-in functions CONS: - incosistent with all the other objects, both permanent & temporary - does not allow shadowing catalog functions Option 2: Special keyword for built-in function I think this is quite similar to the special catalog/db. The thing I am strongly against in this proposal is the GLOBAL keyword. This keyword has a meaning in rdbms systems and means a function that is present for a lifetime of a session in which it was created, but available in all other sessions. Therefore I really don't want to use this keyword in a different context. Option 3: Special catalog/db PROS: - allows shadowing built-in functions - allows shadowing catalog functions - consistent with other objects CONS: - we introduce a special namespace for built-in functions I don't see a problem with introducing the special namespace. In the end it is very similar to the keyword approach. In this case the catalog/db combination would be the "keyword" Therefore my votes: Option 1: -0 Option 2: -1 (I might change to +0 if we can come up with a better keyword) Option 3: +1 Best, Dawid On Thu, 19 Sep 2019, 05:12 Xuefu Z, wrote: > Hi Aljoscha, > > Thanks for the summary and these are great questions to be answered. The > answer to your first question is clear: there is a general agreement to > override built-in functions with temp functions. > > However, your second and third questions are sort of related, as a function > reference can be either just function name (like "func") or in the form or > "cat.db.func". When a reference is just function name, it can mean either a > built-in function or a function defined in the current cat/db. If we > support overriding a built-in function with a temp function, such > overriding can also cover a function in the current cat/db. > > I think what Timo referred as "overriding a catalog function" means a temp > function defined as "cat.db.func" overrides a catalog function "func" in > cat/db even if cat/db is not current. To support this, temp function has to > be tied to a cat/db. What's why I said above that the 2nd and 3rd questions > are related. The problem with such support is the ambiguity when user > defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". > Here "func" can means a global temp function, or a temp function in current > cat/db. If we can assume the former, this creates an inconsistency because > "CREATE FUNCTION func" actually means a function in current cat/db. If we > assume the latter, then there is no way for user to create a global temp > function. > > Giving a special namespace for built-in functions may solve the ambiguity > problem above, but it also introduces artificial catalog/database that > needs special treatment and pollutes the cleanness of the code. I would > rather introduce a syntax in DDL to solve the problem, like "CREATE > [GLOBAL] TEMPORARY FUNCTION func". > > Thus, I'd like to summarize a few candidate proposals for voting purposes: > > 1. Support only global, temporary functions without namespace. Such temp > functions overrides built-in functions and catalog functions in current > cat/db. The resolution order is: temp functions -> built-in functions -> > catalog functions. (Partially or fully qualified functions has no > ambiguity!) > > 2. In addition to #1, support creating and referencing temporary functions > associated with a cat/db with "GLOBAL" qualifier in DDL for global temp > functions. The resolution order is: global temp functions -> built-in > functions -> temp functions in current cat/db -> catalog function. > (Resolution for partially or fully qualified function reference is: temp > functions -> persistent functions.) > > 3. In addition to #1, support creating and referencing temporary functions > associated with a cat/db with a special namespace for built-in functions > and global temp functions. The resolution is the same as #2, except that > the special namespace might be prefixed to a reference to a built-in > function or global temp function. (In absence of the special namespace, the > resolution order is the same as in #2.) > > My personal preference is #1, given the unknown use case and introduced > complexity for #2 and #3. However, #2 is an acceptable alternative. Thus, > my votes are: > > +1 for #1 > +0 for #2 > -1 for #3 > > Everyone, please cast your vote (in above format please!), or let me know > if you have more questions or other candidates. > > Thanks, > Xuefu > > > > > > > > On Wed, Sep 18, 2019 at 6:42 AM Aljoscha Krettek > wrote: > > > Hi, > > > > I think this discussion and the one for FLIP-64 are very connected. To > > resolve the differences, think we have to think about the basic > principles > > and find consensus there. The basic questions I see are: > > > > - Do we want to support overriding builtin functions? > > - Do we want to support overriding catalog
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Aljoscha, Thanks for the summary and these are great questions to be answered. The answer to your first question is clear: there is a general agreement to override built-in functions with temp functions. However, your second and third questions are sort of related, as a function reference can be either just function name (like "func") or in the form or "cat.db.func". When a reference is just function name, it can mean either a built-in function or a function defined in the current cat/db. If we support overriding a built-in function with a temp function, such overriding can also cover a function in the current cat/db. I think what Timo referred as "overriding a catalog function" means a temp function defined as "cat.db.func" overrides a catalog function "func" in cat/db even if cat/db is not current. To support this, temp function has to be tied to a cat/db. What's why I said above that the 2nd and 3rd questions are related. The problem with such support is the ambiguity when user defines a function w/o namespace, "CREATE TEMPORARY FUNCTION func ...". Here "func" can means a global temp function, or a temp function in current cat/db. If we can assume the former, this creates an inconsistency because "CREATE FUNCTION func" actually means a function in current cat/db. If we assume the latter, then there is no way for user to create a global temp function. Giving a special namespace for built-in functions may solve the ambiguity problem above, but it also introduces artificial catalog/database that needs special treatment and pollutes the cleanness of the code. I would rather introduce a syntax in DDL to solve the problem, like "CREATE [GLOBAL] TEMPORARY FUNCTION func". Thus, I'd like to summarize a few candidate proposals for voting purposes: 1. Support only global, temporary functions without namespace. Such temp functions overrides built-in functions and catalog functions in current cat/db. The resolution order is: temp functions -> built-in functions -> catalog functions. (Partially or fully qualified functions has no ambiguity!) 2. In addition to #1, support creating and referencing temporary functions associated with a cat/db with "GLOBAL" qualifier in DDL for global temp functions. The resolution order is: global temp functions -> built-in functions -> temp functions in current cat/db -> catalog function. (Resolution for partially or fully qualified function reference is: temp functions -> persistent functions.) 3. In addition to #1, support creating and referencing temporary functions associated with a cat/db with a special namespace for built-in functions and global temp functions. The resolution is the same as #2, except that the special namespace might be prefixed to a reference to a built-in function or global temp function. (In absence of the special namespace, the resolution order is the same as in #2.) My personal preference is #1, given the unknown use case and introduced complexity for #2 and #3. However, #2 is an acceptable alternative. Thus, my votes are: +1 for #1 +0 for #2 -1 for #3 Everyone, please cast your vote (in above format please!), or let me know if you have more questions or other candidates. Thanks, Xuefu On Wed, Sep 18, 2019 at 6:42 AM Aljoscha Krettek wrote: > Hi, > > I think this discussion and the one for FLIP-64 are very connected. To > resolve the differences, think we have to think about the basic principles > and find consensus there. The basic questions I see are: > > - Do we want to support overriding builtin functions? > - Do we want to support overriding catalog functions? > - And then later: should temporary functions be tied to a > catalog/database? > > I don’t have much to say about these, except that we should somewhat stick > to what the industry does. But I also understand that the industry is > already very divided on this. > > Best, > Aljoscha > > > On 18. Sep 2019, at 11:41, Jark Wu wrote: > > > > Hi, > > > > +1 to strive for reaching consensus on the remaining topics. We are > close to the truth. It will waste a lot of time if we resume the topic some > time later. > > > > +1 to “1-part/override” and I’m also fine with Timo’s “cat.db.fun” way > to override a catalog function. > > > > I’m not sure about “system.system.fun”, it introduces a nonexistent cat > & db? And we still need to do special treatment for the dedicated > system.system cat & db? > > > > Best, > > Jark > > > > > >> 在 2019年9月18日，06:54，Timo Walther 写道： > >> > >> Hi everyone, > >> > >> @Xuefu: I would like to avoid adding too many things incrementally. > Users should be able to override all catalog objects consistently according > to FLIP-64 (Support for Temporary Objects in Table module). If functions > are treated completely different, we need more code and special cases. From > an implementation perspective, this topic only affects the lookup logic > which is rather low implementation effort which is why I would like to > clarify the remaining items. As you
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, I think this discussion and the one for FLIP-64 are very connected. To resolve the differences, think we have to think about the basic principles and find consensus there. The basic questions I see are: - Do we want to support overriding builtin functions? - Do we want to support overriding catalog functions? - And then later: should temporary functions be tied to a catalog/database? I don’t have much to say about these, except that we should somewhat stick to what the industry does. But I also understand that the industry is already very divided on this. Best, Aljoscha > On 18. Sep 2019, at 11:41, Jark Wu wrote: > > Hi, > > +1 to strive for reaching consensus on the remaining topics. We are close to > the truth. It will waste a lot of time if we resume the topic some time > later. > > +1 to “1-part/override” and I’m also fine with Timo’s “cat.db.fun” way to > override a catalog function. > > I’m not sure about “system.system.fun”, it introduces a nonexistent cat & db? > And we still need to do special treatment for the dedicated system.system cat > & db? > > Best, > Jark > > >> 在 2019年9月18日，06:54，Timo Walther 写道： >> >> Hi everyone, >> >> @Xuefu: I would like to avoid adding too many things incrementally. Users >> should be able to override all catalog objects consistently according to >> FLIP-64 (Support for Temporary Objects in Table module). If functions are >> treated completely different, we need more code and special cases. From an >> implementation perspective, this topic only affects the lookup logic which >> is rather low implementation effort which is why I would like to clarify the >> remaining items. As you said, we have a slight consenus on overriding >> built-in functions; we should also strive for reaching consensus on the >> remaining topics. >> >> @Dawid: I like your idea as it ensures registering catalog objects >> consistent and the overriding of built-in functions more explicit. >> >> Thanks, >> Timo >> >> >> On 17.09.19 11:59, kai wang wrote: >>> hi, everyone >>> I think this flip is very meaningful. it supports functions that can be >>> shared by different catalogs and dbs, reducing the duplication of functions. >>> >>> Our group based on flink's sql parser module implements create function >>> feature, stores the parsed function metadata and schema into mysql, and >>> also customizes the catalog, customizes sql-client to support custom >>> schemas and functions. Loaded, but the function is currently global, and is >>> not subdivided according to catalog and db. >>> >>> In addition, I very much hope to participate in the development of this >>> flip, I have been paying attention to the community, but found it is more >>> difficult to join. >>> thank you. >>> >>> Xuefu Z 于2019年9月17日周二 上午11:19写道： >>> Thanks to Tmo and Dawid for sharing thoughts. It seems to me that there is a general consensus on having temp functions that have no namespaces and overwrite built-in functions. (As a side note for comparability, the current user defined functions are all temporary and having no namespaces.) Nevertheless, I can also see the merit of having namespaced temp functions that can overwrite functions defined in a specific cat/db. However, this idea appears orthogonal to the former and can be added incrementally. How about we first implement non-namespaced temp functions now and leave the door open for namespaced ones for later releases as the requirement might become more crystal? This also helps shorten the debate and allow us to make some progress along this direction. As to Dawid's idea of having a dedicated cat/db to host the temporary temp functions that don't have namespaces, my only concern is the special treatment for a cat/db, which makes code less clean, as evident in treating the built-in catalog currently. Thanks, Xuefiu On Mon, Sep 16, 2019 at 5:07 PM Dawid Wysakowicz < wysakowicz.da...@gmail.com> wrote: > Hi, > Another idea to consider on top of Timo's suggestion. How about we have a > special namespace (catalog + database) for built-in objects? This catalog > would be invisible for users as Xuefu was suggesting. > > Then users could still override built-in functions, if they fully qualify > object with the built-in namespace, but by default the common logic of > current dB & cat would be used. > > CREATE TEMPORARY FUNCTION func ... > registers temporary function in current cat & dB > > CREATE TEMPORARY FUNCTION cat.db.func ... > registers temporary function in cat db > > CREATE TEMPORARY FUNCTION system.system.func ... > Overrides built-in function with temporary function > > The built-in/system namespace would not be writable for permanent objects. > WDYT? > > This way I think we can
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, +1 to strive for reaching consensus on the remaining topics. We are close to the truth. It will waste a lot of time if we resume the topic some time later. +1 to “1-part/override” and I’m also fine with Timo’s “cat.db.fun” way to override a catalog function. I’m not sure about “system.system.fun”, it introduces a nonexistent cat & db? And we still need to do special treatment for the dedicated system.system cat & db? Best, Jark > 在 2019年9月18日，06:54，Timo Walther 写道： > > Hi everyone, > > @Xuefu: I would like to avoid adding too many things incrementally. Users > should be able to override all catalog objects consistently according to > FLIP-64 (Support for Temporary Objects in Table module). If functions are > treated completely different, we need more code and special cases. From an > implementation perspective, this topic only affects the lookup logic which is > rather low implementation effort which is why I would like to clarify the > remaining items. As you said, we have a slight consenus on overriding > built-in functions; we should also strive for reaching consensus on the > remaining topics. > > @Dawid: I like your idea as it ensures registering catalog objects consistent > and the overriding of built-in functions more explicit. > > Thanks, > Timo > > > On 17.09.19 11:59, kai wang wrote: >> hi, everyone >> I think this flip is very meaningful. it supports functions that can be >> shared by different catalogs and dbs, reducing the duplication of functions. >> >> Our group based on flink's sql parser module implements create function >> feature, stores the parsed function metadata and schema into mysql, and >> also customizes the catalog, customizes sql-client to support custom >> schemas and functions. Loaded, but the function is currently global, and is >> not subdivided according to catalog and db. >> >> In addition, I very much hope to participate in the development of this >> flip, I have been paying attention to the community, but found it is more >> difficult to join. >> thank you. >> >> Xuefu Z 于2019年9月17日周二 上午11:19写道： >> >>> Thanks to Tmo and Dawid for sharing thoughts. >>> >>> It seems to me that there is a general consensus on having temp functions >>> that have no namespaces and overwrite built-in functions. (As a side note >>> for comparability, the current user defined functions are all temporary and >>> having no namespaces.) >>> >>> Nevertheless, I can also see the merit of having namespaced temp functions >>> that can overwrite functions defined in a specific cat/db. However, this >>> idea appears orthogonal to the former and can be added incrementally. >>> >>> How about we first implement non-namespaced temp functions now and leave >>> the door open for namespaced ones for later releases as the requirement >>> might become more crystal? This also helps shorten the debate and allow us >>> to make some progress along this direction. >>> >>> As to Dawid's idea of having a dedicated cat/db to host the temporary temp >>> functions that don't have namespaces, my only concern is the special >>> treatment for a cat/db, which makes code less clean, as evident in treating >>> the built-in catalog currently. >>> >>> Thanks, >>> Xuefiu >>> >>> On Mon, Sep 16, 2019 at 5:07 PM Dawid Wysakowicz < >>> wysakowicz.da...@gmail.com> >>> wrote: >>> Hi, Another idea to consider on top of Timo's suggestion. How about we have a special namespace (catalog + database) for built-in objects? This catalog would be invisible for users as Xuefu was suggesting. Then users could still override built-in functions, if they fully qualify object with the built-in namespace, but by default the common logic of current dB & cat would be used. CREATE TEMPORARY FUNCTION func ... registers temporary function in current cat & dB CREATE TEMPORARY FUNCTION cat.db.func ... registers temporary function in cat db CREATE TEMPORARY FUNCTION system.system.func ... Overrides built-in function with temporary function The built-in/system namespace would not be writable for permanent >>> objects. WDYT? This way I think we can have benefits of both solutions. Best, Dawid On Tue, 17 Sep 2019, 07:24 Timo Walther, wrote: > Hi Bowen, > > I understand the potential benefit of overriding certain built-in > functions. I'm open to such a feature if many people agree. However, it > would be great to still support overriding catalog functions with > temporary functions in order to prototype a query even though a > catalog/database might not be available currently or should not be > modified yet. How about we support both cases? > > CREATE TEMPORARY FUNCTION abs > -> creates/overrides a built-in function and never consideres current > catalog and database; inconsistent with other DDL but acceptable for
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi everyone, @Xuefu: I would like to avoid adding too many things incrementally. Users should be able to override all catalog objects consistently according to FLIP-64 (Support for Temporary Objects in Table module). If functions are treated completely different, we need more code and special cases. From an implementation perspective, this topic only affects the lookup logic which is rather low implementation effort which is why I would like to clarify the remaining items. As you said, we have a slight consenus on overriding built-in functions; we should also strive for reaching consensus on the remaining topics. @Dawid: I like your idea as it ensures registering catalog objects consistent and the overriding of built-in functions more explicit. Thanks, Timo On 17.09.19 11:59, kai wang wrote: hi, everyone I think this flip is very meaningful. it supports functions that can be shared by different catalogs and dbs, reducing the duplication of functions. Our group based on flink's sql parser module implements create function feature, stores the parsed function metadata and schema into mysql, and also customizes the catalog, customizes sql-client to support custom schemas and functions. Loaded, but the function is currently global, and is not subdivided according to catalog and db. In addition, I very much hope to participate in the development of this flip, I have been paying attention to the community, but found it is more difficult to join. thank you. Xuefu Z 于2019年9月17日周二 上午11:19写道： Thanks to Tmo and Dawid for sharing thoughts. It seems to me that there is a general consensus on having temp functions that have no namespaces and overwrite built-in functions. (As a side note for comparability, the current user defined functions are all temporary and having no namespaces.) Nevertheless, I can also see the merit of having namespaced temp functions that can overwrite functions defined in a specific cat/db. However, this idea appears orthogonal to the former and can be added incrementally. How about we first implement non-namespaced temp functions now and leave the door open for namespaced ones for later releases as the requirement might become more crystal? This also helps shorten the debate and allow us to make some progress along this direction. As to Dawid's idea of having a dedicated cat/db to host the temporary temp functions that don't have namespaces, my only concern is the special treatment for a cat/db, which makes code less clean, as evident in treating the built-in catalog currently. Thanks, Xuefiu On Mon, Sep 16, 2019 at 5:07 PM Dawid Wysakowicz < wysakowicz.da...@gmail.com> wrote: Hi, Another idea to consider on top of Timo's suggestion. How about we have a special namespace (catalog + database) for built-in objects? This catalog would be invisible for users as Xuefu was suggesting. Then users could still override built-in functions, if they fully qualify object with the built-in namespace, but by default the common logic of current dB & cat would be used. CREATE TEMPORARY FUNCTION func ... registers temporary function in current cat & dB CREATE TEMPORARY FUNCTION cat.db.func ... registers temporary function in cat db CREATE TEMPORARY FUNCTION system.system.func ... Overrides built-in function with temporary function The built-in/system namespace would not be writable for permanent objects. WDYT? This way I think we can have benefits of both solutions. Best, Dawid On Tue, 17 Sep 2019, 07:24 Timo Walther, wrote: Hi Bowen, I understand the potential benefit of overriding certain built-in functions. I'm open to such a feature if many people agree. However, it would be great to still support overriding catalog functions with temporary functions in order to prototype a query even though a catalog/database might not be available currently or should not be modified yet. How about we support both cases? CREATE TEMPORARY FUNCTION abs -> creates/overrides a built-in function and never consideres current catalog and database; inconsistent with other DDL but acceptable for functions I guess. CREATE TEMPORARY FUNCTION cat.db.fun -> creates/overrides a catalog function Regarding "Flink don't have any other built-in objects (tables, views) except functions", this might change in the near future. Take https://issues.apache.org/jira/browse/FLINK-13900 as an example. Thanks, Timo On 14.09.19 01:40, Bowen Li wrote: Hi Fabian, Yes, I agree 1-part/no-override is the least favorable thus I didn't include that as a voting option, and the discussion is mainly between 1-part/override builtin and 3-part/not override builtin. Re > However, it means that temp functions are differently treated than other db objects. IMO, the treatment difference results from the fact that functions are a bit different from other objects - Flink don't have any other built-in objects (tables, views) except functions. Cheers, Bowen -- Xuefu Zhang "In Honey We Trust!"
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
hi, everyone I think this flip is very meaningful. it supports functions that can be shared by different catalogs and dbs, reducing the duplication of functions. Our group based on flink's sql parser module implements create function feature, stores the parsed function metadata and schema into mysql, and also customizes the catalog, customizes sql-client to support custom schemas and functions. Loaded, but the function is currently global, and is not subdivided according to catalog and db. In addition, I very much hope to participate in the development of this flip, I have been paying attention to the community, but found it is more difficult to join. thank you. Xuefu Z 于2019年9月17日周二 上午11:19写道： > Thanks to Tmo and Dawid for sharing thoughts. > > It seems to me that there is a general consensus on having temp functions > that have no namespaces and overwrite built-in functions. (As a side note > for comparability, the current user defined functions are all temporary and > having no namespaces.) > > Nevertheless, I can also see the merit of having namespaced temp functions > that can overwrite functions defined in a specific cat/db. However, this > idea appears orthogonal to the former and can be added incrementally. > > How about we first implement non-namespaced temp functions now and leave > the door open for namespaced ones for later releases as the requirement > might become more crystal? This also helps shorten the debate and allow us > to make some progress along this direction. > > As to Dawid's idea of having a dedicated cat/db to host the temporary temp > functions that don't have namespaces, my only concern is the special > treatment for a cat/db, which makes code less clean, as evident in treating > the built-in catalog currently. > > Thanks, > Xuefiu > > On Mon, Sep 16, 2019 at 5:07 PM Dawid Wysakowicz < > wysakowicz.da...@gmail.com> > wrote: > > > Hi, > > Another idea to consider on top of Timo's suggestion. How about we have a > > special namespace (catalog + database) for built-in objects? This catalog > > would be invisible for users as Xuefu was suggesting. > > > > Then users could still override built-in functions, if they fully qualify > > object with the built-in namespace, but by default the common logic of > > current dB & cat would be used. > > > > CREATE TEMPORARY FUNCTION func ... > > registers temporary function in current cat & dB > > > > CREATE TEMPORARY FUNCTION cat.db.func ... > > registers temporary function in cat db > > > > CREATE TEMPORARY FUNCTION system.system.func ... > > Overrides built-in function with temporary function > > > > The built-in/system namespace would not be writable for permanent > objects. > > WDYT? > > > > This way I think we can have benefits of both solutions. > > > > Best, > > Dawid > > > > > > On Tue, 17 Sep 2019, 07:24 Timo Walther, wrote: > > > > > Hi Bowen, > > > > > > I understand the potential benefit of overriding certain built-in > > > functions. I'm open to such a feature if many people agree. However, it > > > would be great to still support overriding catalog functions with > > > temporary functions in order to prototype a query even though a > > > catalog/database might not be available currently or should not be > > > modified yet. How about we support both cases? > > > > > > CREATE TEMPORARY FUNCTION abs > > > -> creates/overrides a built-in function and never consideres current > > > catalog and database; inconsistent with other DDL but acceptable for > > > functions I guess. > > > CREATE TEMPORARY FUNCTION cat.db.fun > > > -> creates/overrides a catalog function > > > > > > Regarding "Flink don't have any other built-in objects (tables, views) > > > except functions", this might change in the near future. Take > > > https://issues.apache.org/jira/browse/FLINK-13900 as an example. > > > > > > Thanks, > > > Timo > > > > > > On 14.09.19 01:40, Bowen Li wrote: > > > > Hi Fabian, > > > > > > > > Yes, I agree 1-part/no-override is the least favorable thus I didn't > > > > include that as a voting option, and the discussion is mainly between > > > > 1-part/override builtin and 3-part/not override builtin. > > > > > > > > Re > However, it means that temp functions are differently treated > than > > > > other db objects. > > > > IMO, the treatment difference results from the fact that functions > are > > a > > > > bit different from other objects - Flink don't have any other > built-in > > > > objects (tables, views) except functions. > > > > > > > > Cheers, > > > > Bowen > > > > > > > > > > > > > > > -- > Xuefu Zhang > > "In Honey We Trust!" >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks to Tmo and Dawid for sharing thoughts. It seems to me that there is a general consensus on having temp functions that have no namespaces and overwrite built-in functions. (As a side note for comparability, the current user defined functions are all temporary and having no namespaces.) Nevertheless, I can also see the merit of having namespaced temp functions that can overwrite functions defined in a specific cat/db. However, this idea appears orthogonal to the former and can be added incrementally. How about we first implement non-namespaced temp functions now and leave the door open for namespaced ones for later releases as the requirement might become more crystal? This also helps shorten the debate and allow us to make some progress along this direction. As to Dawid's idea of having a dedicated cat/db to host the temporary temp functions that don't have namespaces, my only concern is the special treatment for a cat/db, which makes code less clean, as evident in treating the built-in catalog currently. Thanks, Xuefiu On Mon, Sep 16, 2019 at 5:07 PM Dawid Wysakowicz wrote: > Hi, > Another idea to consider on top of Timo's suggestion. How about we have a > special namespace (catalog + database) for built-in objects? This catalog > would be invisible for users as Xuefu was suggesting. > > Then users could still override built-in functions, if they fully qualify > object with the built-in namespace, but by default the common logic of > current dB & cat would be used. > > CREATE TEMPORARY FUNCTION func ... > registers temporary function in current cat & dB > > CREATE TEMPORARY FUNCTION cat.db.func ... > registers temporary function in cat db > > CREATE TEMPORARY FUNCTION system.system.func ... > Overrides built-in function with temporary function > > The built-in/system namespace would not be writable for permanent objects. > WDYT? > > This way I think we can have benefits of both solutions. > > Best, > Dawid > > > On Tue, 17 Sep 2019, 07:24 Timo Walther, wrote: > > > Hi Bowen, > > > > I understand the potential benefit of overriding certain built-in > > functions. I'm open to such a feature if many people agree. However, it > > would be great to still support overriding catalog functions with > > temporary functions in order to prototype a query even though a > > catalog/database might not be available currently or should not be > > modified yet. How about we support both cases? > > > > CREATE TEMPORARY FUNCTION abs > > -> creates/overrides a built-in function and never consideres current > > catalog and database; inconsistent with other DDL but acceptable for > > functions I guess. > > CREATE TEMPORARY FUNCTION cat.db.fun > > -> creates/overrides a catalog function > > > > Regarding "Flink don't have any other built-in objects (tables, views) > > except functions", this might change in the near future. Take > > https://issues.apache.org/jira/browse/FLINK-13900 as an example. > > > > Thanks, > > Timo > > > > On 14.09.19 01:40, Bowen Li wrote: > > > Hi Fabian, > > > > > > Yes, I agree 1-part/no-override is the least favorable thus I didn't > > > include that as a voting option, and the discussion is mainly between > > > 1-part/override builtin and 3-part/not override builtin. > > > > > > Re > However, it means that temp functions are differently treated than > > > other db objects. > > > IMO, the treatment difference results from the fact that functions are > a > > > bit different from other objects - Flink don't have any other built-in > > > objects (tables, views) except functions. > > > > > > Cheers, > > > Bowen > > > > > > > > -- Xuefu Zhang "In Honey We Trust!"
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, Another idea to consider on top of Timo's suggestion. How about we have a special namespace (catalog + database) for built-in objects? This catalog would be invisible for users as Xuefu was suggesting. Then users could still override built-in functions, if they fully qualify object with the built-in namespace, but by default the common logic of current dB & cat would be used. CREATE TEMPORARY FUNCTION func ... registers temporary function in current cat & dB CREATE TEMPORARY FUNCTION cat.db.func ... registers temporary function in cat db CREATE TEMPORARY FUNCTION system.system.func ... Overrides built-in function with temporary function The built-in/system namespace would not be writable for permanent objects. WDYT? This way I think we can have benefits of both solutions. Best, Dawid On Tue, 17 Sep 2019, 07:24 Timo Walther, wrote: > Hi Bowen, > > I understand the potential benefit of overriding certain built-in > functions. I'm open to such a feature if many people agree. However, it > would be great to still support overriding catalog functions with > temporary functions in order to prototype a query even though a > catalog/database might not be available currently or should not be > modified yet. How about we support both cases? > > CREATE TEMPORARY FUNCTION abs > -> creates/overrides a built-in function and never consideres current > catalog and database; inconsistent with other DDL but acceptable for > functions I guess. > CREATE TEMPORARY FUNCTION cat.db.fun > -> creates/overrides a catalog function > > Regarding "Flink don't have any other built-in objects (tables, views) > except functions", this might change in the near future. Take > https://issues.apache.org/jira/browse/FLINK-13900 as an example. > > Thanks, > Timo > > On 14.09.19 01:40, Bowen Li wrote: > > Hi Fabian, > > > > Yes, I agree 1-part/no-override is the least favorable thus I didn't > > include that as a voting option, and the discussion is mainly between > > 1-part/override builtin and 3-part/not override builtin. > > > > Re > However, it means that temp functions are differently treated than > > other db objects. > > IMO, the treatment difference results from the fact that functions are a > > bit different from other objects - Flink don't have any other built-in > > objects (tables, views) except functions. > > > > Cheers, > > Bowen > > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Bowen, I understand the potential benefit of overriding certain built-in functions. I'm open to such a feature if many people agree. However, it would be great to still support overriding catalog functions with temporary functions in order to prototype a query even though a catalog/database might not be available currently or should not be modified yet. How about we support both cases? CREATE TEMPORARY FUNCTION abs -> creates/overrides a built-in function and never consideres current catalog and database; inconsistent with other DDL but acceptable for functions I guess. CREATE TEMPORARY FUNCTION cat.db.fun -> creates/overrides a catalog function Regarding "Flink don't have any other built-in objects (tables, views) except functions", this might change in the near future. Take https://issues.apache.org/jira/browse/FLINK-13900 as an example. Thanks, Timo On 14.09.19 01:40, Bowen Li wrote: Hi Fabian, Yes, I agree 1-part/no-override is the least favorable thus I didn't include that as a voting option, and the discussion is mainly between 1-part/override builtin and 3-part/not override builtin. Re > However, it means that temp functions are differently treated than other db objects. IMO, the treatment difference results from the fact that functions are a bit different from other objects - Flink don't have any other built-in objects (tables, views) except functions. Cheers, Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Fabian, Yes, I agree 1-part/no-override is the least favorable thus I didn't include that as a voting option, and the discussion is mainly between 1-part/override builtin and 3-part/not override builtin. Re > However, it means that temp functions are differently treated than other db objects. IMO, the treatment difference results from the fact that functions are a bit different from other objects - Flink don't have any other built-in objects (tables, views) except functions. Cheers, Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all, Thanks Dawid for the additional explanation! As others summarized there are two questions: 1) Are temporal functions a) top-level functions (1-part address) and not associated with a catalog/db or b) do we threat them like any other database object with a 3-part address. 2) If we treat them as top-level functions, do we a) allow overriding built-in functions (by giving preference over built-in functions) or b) not. >From that, we can have three combinations: 1-part/override: It has the (IMO) benefit of allowing to change the default behavior of Flink SQL by overriding built-in functions. However, it means that temp functions are differently treated than other db objects. 1-part/no-override: Unambiguous function resolution, special treatment for temp functions 3-part: No special treatment of temp functions, but also no way to change the semantics of a built-in function (unambiguous semantics) In fact, I don't have strong preference for any of the choices but 1-part/no-override would be my least favorite (no gains but special treatment of temp functions). All have pros and cons and can be justified. Cheers, Fabian Am Mi., 11. Sept. 2019 um 20:52 Uhr schrieb Bowen Li : > Hi, > > Thanks @Fabian @Dawid and everyone else for sharing your thoughts! > > First, I'd like to take Hive built-in functions out of this FLIP to keep > our original scope and make it less controversial on a potential modular > approach. I will remove Hive built-in functions from the google doc. > > Then the focus of debate is mainly function resolution order and temp > function namespace, which are somewhat related. I roughly summarized this > thread, and currently we are debating on two approaches with preference > from the following people: > > Option 1: > Proposal: temp functions will be of 1-part path (function name only), > and can override built-in functions. The ambiguous function resolution > order is thus 1) temp functions 2) built-in functions 3) catalog functions > in the current catalog/database > Votes: Xuefu, Bowen, Fabian, Jark > > Option 2: > Proposal: temp functions will be of 3-part path (with catalog, > database, and function name), and temp functions cannot override built-in > functions. The ambiguous function resolution order is thus 1) built-in > functions 2) temp functions (in 3-part path) 3) catalog functions in the > current catalog/database > Votes: Dawid, Timo > > > Do you think we need a separate voting thread on the two options in the > community, or are we able to conclude from the above summary? > > > > On Wed, Sep 11, 2019 at 8:09 AM Dawid Wysakowicz > wrote: > > > Hi Fabian, > > Thank you for your response. > > Regarding the temporary function, just wanted to clarify one thing: the > > 3-part identifier does not mean the user always has to provide the > catalog > > & database explicitly. The same way user does not have to provide them in > > e.g. when creating permanent table, view etc. It means though functions > are > > always stored within a database. The same way as all the permanent > objects > > and other temporary objects(tables, views). If not given explicitly the > > current catalog & database would be used, both in the create statement or > > when using the function. > > > > Point taken though your preference would be to support overriding > built-in > > functions. > > > > Best, > > Dawid > > > > On Wed, 11 Sep 2019, 21:14 Fabian Hueske, wrote: > > > > > Hi all, > > > > > > I'd like to add my opinion on this topic as well ;-) > > > > > > In general, I think overriding built-in function with temp functions > has > > a > > > couple of benefits but also a few challenges: > > > > > > * Users can reimplement the behavior of a built-in functions of a > > different > > > system, e.g., for backward compatibility after a migration. > > > * I don't think that "accidental" overrides and surprising semantics > are > > an > > > issue or dangerous. The user registered the temp function in the same > > > session and should therefore be aware of the changed semantics. > > > * I see that not all built-in functions can be overridden, like the > CAST > > > example that Dawid gave. However, I think these should be a small > > fraction > > > and such functions could be blacklisted. Sure, that's not super > > consistent, > > > but should (IMO) not be a big issue in practice. > > > * Temp functions should be easy to use. Requiring a 3-part addressing > > makes > > > them a lot less user friendly, IMO. Users need to think about what > > catalog > > > and db to choose when registering them. Also using a temp function in a > > > query becomes less convenient. Moreover, I agree with Bowen's concerns > > that > > > a 3-part addressing scheme reduces the temporal appearance of the > > function. > > > > > > From the three possible solutions, my preference order is > > > 1) 1-part address with override of built-in > > > 2) 1-part address without override of built-in > > > 3) 3-part address
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi,
Thanks @Fabian @Dawid and everyone else for sharing your thoughts!
First, I'd like to take Hive built-in functions out of this FLIP to keep
our original scope and make it less controversial on a potential modular
approach. I will remove Hive built-in functions from the google doc.
Then the focus of debate is mainly function resolution order and temp
function namespace, which are somewhat related. I roughly summarized this
thread, and currently we are debating on two approaches with preference
from the following people:
Option 1:
Proposal: temp functions will be of 1-part path (function name only),
and can override built-in functions. The ambiguous function resolution
order is thus 1) temp functions 2) built-in functions 3) catalog functions
in the current catalog/database
Votes: Xuefu, Bowen, Fabian, Jark
Option 2:
Proposal: temp functions will be of 3-part path (with catalog,
database, and function name), and temp functions cannot override built-in
functions. The ambiguous function resolution order is thus 1) built-in
functions 2) temp functions (in 3-part path) 3) catalog functions in the
current catalog/database
Votes: Dawid, Timo
Do you think we need a separate voting thread on the two options in the
community, or are we able to conclude from the above summary?
On Wed, Sep 11, 2019 at 8:09 AM Dawid Wysakowicz
wrote:
> Hi Fabian,
> Thank you for your response.
> Regarding the temporary function, just wanted to clarify one thing: the
> 3-part identifier does not mean the user always has to provide the catalog
> & database explicitly. The same way user does not have to provide them in
> e.g. when creating permanent table, view etc. It means though functions are
> always stored within a database. The same way as all the permanent objects
> and other temporary objects(tables, views). If not given explicitly the
> current catalog & database would be used, both in the create statement or
> when using the function.
>
> Point taken though your preference would be to support overriding built-in
> functions.
>
> Best,
> Dawid
>
> On Wed, 11 Sep 2019, 21:14 Fabian Hueske, wrote:
>
> > Hi all,
> >
> > I'd like to add my opinion on this topic as well ;-)
> >
> > In general, I think overriding built-in function with temp functions has
> a
> > couple of benefits but also a few challenges:
> >
> > * Users can reimplement the behavior of a built-in functions of a
> different
> > system, e.g., for backward compatibility after a migration.
> > * I don't think that "accidental" overrides and surprising semantics are
> an
> > issue or dangerous. The user registered the temp function in the same
> > session and should therefore be aware of the changed semantics.
> > * I see that not all built-in functions can be overridden, like the CAST
> > example that Dawid gave. However, I think these should be a small
> fraction
> > and such functions could be blacklisted. Sure, that's not super
> consistent,
> > but should (IMO) not be a big issue in practice.
> > * Temp functions should be easy to use. Requiring a 3-part addressing
> makes
> > them a lot less user friendly, IMO. Users need to think about what
> catalog
> > and db to choose when registering them. Also using a temp function in a
> > query becomes less convenient. Moreover, I agree with Bowen's concerns
> that
> > a 3-part addressing scheme reduces the temporal appearance of the
> function.
> >
> > From the three possible solutions, my preference order is
> > 1) 1-part address with override of built-in
> > 2) 1-part address without override of built-in
> > 3) 3-part address
> >
> > Regarding the issue of external built-in functions, I don't think that
> > Timo's proposal of modules is fully orthogonal to this discussion.
> > A Hive function module could be an alternative to offering Hive functions
> > as part of Hive's catalog.
> > From a user's point of view, I think that modules would be a "cleaner"
> > integration ("Why do I need a Hive catalog if all I want to do is apply a
> > Hive function on a Kafka table?").
> > However, the module approach clearly has the problem of dealing with
> > same-named functions in different modules (e.g., a Hive function and a
> > Flink built-in function).
> > The catalog approach as the benefit that functions can be addressed like
> > hiveCat::func (or a similar path).
> >
> > I'm not sure what's the best solution here.
> >
> > Cheers,
> > Fabian
> >
> >
> > Am Mo., 9. Sept. 2019 um 06:30 Uhr schrieb Bowen Li >:
> >
> > > Hi,
> > >
> > > W.r.t temp functions, I feel both options have their benefits and can
> > > theoretically achieve similar functionalities one way or another. In
> the
> > > end, it's more about use cases, users habits, and trade-offs.
> > >
> > > Re> Not always users are in full control of the catalog functions.
> There
> > is
> > > also the case where different teams manage the catalog & use the
> catalog.
> > >
> > > Temp functions live within a session, and not within a catalog.
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Fabian,
Thank you for your response.
Regarding the temporary function, just wanted to clarify one thing: the
3-part identifier does not mean the user always has to provide the catalog
& database explicitly. The same way user does not have to provide them in
e.g. when creating permanent table, view etc. It means though functions are
always stored within a database. The same way as all the permanent objects
and other temporary objects(tables, views). If not given explicitly the
current catalog & database would be used, both in the create statement or
when using the function.
Point taken though your preference would be to support overriding built-in
functions.
Best,
Dawid
On Wed, 11 Sep 2019, 21:14 Fabian Hueske, wrote:
> Hi all,
>
> I'd like to add my opinion on this topic as well ;-)
>
> In general, I think overriding built-in function with temp functions has a
> couple of benefits but also a few challenges:
>
> * Users can reimplement the behavior of a built-in functions of a different
> system, e.g., for backward compatibility after a migration.
> * I don't think that "accidental" overrides and surprising semantics are an
> issue or dangerous. The user registered the temp function in the same
> session and should therefore be aware of the changed semantics.
> * I see that not all built-in functions can be overridden, like the CAST
> example that Dawid gave. However, I think these should be a small fraction
> and such functions could be blacklisted. Sure, that's not super consistent,
> but should (IMO) not be a big issue in practice.
> * Temp functions should be easy to use. Requiring a 3-part addressing makes
> them a lot less user friendly, IMO. Users need to think about what catalog
> and db to choose when registering them. Also using a temp function in a
> query becomes less convenient. Moreover, I agree with Bowen's concerns that
> a 3-part addressing scheme reduces the temporal appearance of the function.
>
> From the three possible solutions, my preference order is
> 1) 1-part address with override of built-in
> 2) 1-part address without override of built-in
> 3) 3-part address
>
> Regarding the issue of external built-in functions, I don't think that
> Timo's proposal of modules is fully orthogonal to this discussion.
> A Hive function module could be an alternative to offering Hive functions
> as part of Hive's catalog.
> From a user's point of view, I think that modules would be a "cleaner"
> integration ("Why do I need a Hive catalog if all I want to do is apply a
> Hive function on a Kafka table?").
> However, the module approach clearly has the problem of dealing with
> same-named functions in different modules (e.g., a Hive function and a
> Flink built-in function).
> The catalog approach as the benefit that functions can be addressed like
> hiveCat::func (or a similar path).
>
> I'm not sure what's the best solution here.
>
> Cheers,
> Fabian
>
>
> Am Mo., 9. Sept. 2019 um 06:30 Uhr schrieb Bowen Li :
>
> > Hi,
> >
> > W.r.t temp functions, I feel both options have their benefits and can
> > theoretically achieve similar functionalities one way or another. In the
> > end, it's more about use cases, users habits, and trade-offs.
> >
> > Re> Not always users are in full control of the catalog functions. There
> is
> > also the case where different teams manage the catalog & use the catalog.
> >
> > Temp functions live within a session, and not within a catalog. Having
> > 3-part paths may implies temp functions are tied to a catalog in two
> > aspects.
> > 1) it may indicate each catalog manages their temp functions, which is
> not
> > true as we seem all agree they should reside at a central place, either
> in
> > FunctionCatalog or CatalogManager
> > 2) it may indicate there's some access control. When users are forbidden
> to
> > manipulate some objects in the catalog that's managed by other teams, but
> > are allowed to manipulate some other objects (temp functions in this
> case)
> > belonging to the catalog in namespaces, users may think we introduced
> extra
> > complexity and confusion with some kind of access control into the
> problem.
> > It doesn't feel intuitive enough for end users.
> >
> > Thus, I'd be in favor of 1-part path for temporary functions, and other
> > temp objects.
> >
> > Thanks,
> > Bowen
> >
> >
> >
> > On Fri, Sep 6, 2019 at 2:16 AM Dawid Wysakowicz
> > wrote:
> >
> > > I agree the consequences of the decision are substantial. Let's see
> what
> > > others think.
> > >
> > > -- Catalog functions are defined by users, and we suppose they can
> > > drop/alter it in any way they want. Thus, overwriting a catalog
> function
> > > doesn't seem to be a strong use case that we should be concerned about.
> > > Rather, there are known use case for overwriting built-in functions.
> > >
> > > Not always users are in full control of the catalog functions. There is
> > > also the case where different teams manage the catalog & use the
> catalog.
> > > As for
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all,
I'd like to add my opinion on this topic as well ;-)
In general, I think overriding built-in function with temp functions has a
couple of benefits but also a few challenges:
* Users can reimplement the behavior of a built-in functions of a different
system, e.g., for backward compatibility after a migration.
* I don't think that "accidental" overrides and surprising semantics are an
issue or dangerous. The user registered the temp function in the same
session and should therefore be aware of the changed semantics.
* I see that not all built-in functions can be overridden, like the CAST
example that Dawid gave. However, I think these should be a small fraction
and such functions could be blacklisted. Sure, that's not super consistent,
but should (IMO) not be a big issue in practice.
* Temp functions should be easy to use. Requiring a 3-part addressing makes
them a lot less user friendly, IMO. Users need to think about what catalog
and db to choose when registering them. Also using a temp function in a
query becomes less convenient. Moreover, I agree with Bowen's concerns that
a 3-part addressing scheme reduces the temporal appearance of the function.
>From the three possible solutions, my preference order is
1) 1-part address with override of built-in
2) 1-part address without override of built-in
3) 3-part address
Regarding the issue of external built-in functions, I don't think that
Timo's proposal of modules is fully orthogonal to this discussion.
A Hive function module could be an alternative to offering Hive functions
as part of Hive's catalog.
>From a user's point of view, I think that modules would be a "cleaner"
integration ("Why do I need a Hive catalog if all I want to do is apply a
Hive function on a Kafka table?").
However, the module approach clearly has the problem of dealing with
same-named functions in different modules (e.g., a Hive function and a
Flink built-in function).
The catalog approach as the benefit that functions can be addressed like
hiveCat::func (or a similar path).
I'm not sure what's the best solution here.
Cheers,
Fabian
Am Mo., 9. Sept. 2019 um 06:30 Uhr schrieb Bowen Li :
> Hi,
>
> W.r.t temp functions, I feel both options have their benefits and can
> theoretically achieve similar functionalities one way or another. In the
> end, it's more about use cases, users habits, and trade-offs.
>
> Re> Not always users are in full control of the catalog functions. There is
> also the case where different teams manage the catalog & use the catalog.
>
> Temp functions live within a session, and not within a catalog. Having
> 3-part paths may implies temp functions are tied to a catalog in two
> aspects.
> 1) it may indicate each catalog manages their temp functions, which is not
> true as we seem all agree they should reside at a central place, either in
> FunctionCatalog or CatalogManager
> 2) it may indicate there's some access control. When users are forbidden to
> manipulate some objects in the catalog that's managed by other teams, but
> are allowed to manipulate some other objects (temp functions in this case)
> belonging to the catalog in namespaces, users may think we introduced extra
> complexity and confusion with some kind of access control into the problem.
> It doesn't feel intuitive enough for end users.
>
> Thus, I'd be in favor of 1-part path for temporary functions, and other
> temp objects.
>
> Thanks,
> Bowen
>
>
>
> On Fri, Sep 6, 2019 at 2:16 AM Dawid Wysakowicz
> wrote:
>
> > I agree the consequences of the decision are substantial. Let's see what
> > others think.
> >
> > -- Catalog functions are defined by users, and we suppose they can
> > drop/alter it in any way they want. Thus, overwriting a catalog function
> > doesn't seem to be a strong use case that we should be concerned about.
> > Rather, there are known use case for overwriting built-in functions.
> >
> > Not always users are in full control of the catalog functions. There is
> > also the case where different teams manage the catalog & use the catalog.
> > As for overriding built-in functions with 3-part approach user can always
> > use an equally named function from a catalog. E.g. to override
> >
> > *SELECT explode(arr) FROM ...*
> >
> > user can always write:
> >
> > *SELECT db.explode(arr) FROM ...*
> >
> > Best,
> >
> > Dawid
> > On 06/09/2019 10:54, Xuefu Z wrote:
> >
> > Hi Dawid,
> >
> > Thank you for your summary. While the only difference in the two
> proposals
> > is one- or three-part in naming, the consequence would be substantial.
> >
> > To me, there are two major use cases of temporary functions compared to
> > persistent ones:
> > 1. Temporary in nature and auto managed by the session. More often than
> > not, admin doesn't even allow user to create persistent functions.
> > 2. Provide an opportunity to overwriting system built-in functions.
> >
> > Since built-in functions has one-part name, requiring three-part name for
> > temporary functions
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, W.r.t temp functions, I feel both options have their benefits and can theoretically achieve similar functionalities one way or another. In the end, it's more about use cases, users habits, and trade-offs. Re> Not always users are in full control of the catalog functions. There is also the case where different teams manage the catalog & use the catalog. Temp functions live within a session, and not within a catalog. Having 3-part paths may implies temp functions are tied to a catalog in two aspects. 1) it may indicate each catalog manages their temp functions, which is not true as we seem all agree they should reside at a central place, either in FunctionCatalog or CatalogManager 2) it may indicate there's some access control. When users are forbidden to manipulate some objects in the catalog that's managed by other teams, but are allowed to manipulate some other objects (temp functions in this case) belonging to the catalog in namespaces, users may think we introduced extra complexity and confusion with some kind of access control into the problem. It doesn't feel intuitive enough for end users. Thus, I'd be in favor of 1-part path for temporary functions, and other temp objects. Thanks, Bowen On Fri, Sep 6, 2019 at 2:16 AM Dawid Wysakowicz wrote: > I agree the consequences of the decision are substantial. Let's see what > others think. > > -- Catalog functions are defined by users, and we suppose they can > drop/alter it in any way they want. Thus, overwriting a catalog function > doesn't seem to be a strong use case that we should be concerned about. > Rather, there are known use case for overwriting built-in functions. > > Not always users are in full control of the catalog functions. There is > also the case where different teams manage the catalog & use the catalog. > As for overriding built-in functions with 3-part approach user can always > use an equally named function from a catalog. E.g. to override > > *SELECT explode(arr) FROM ...* > > user can always write: > > *SELECT db.explode(arr) FROM ...* > > Best, > > Dawid > On 06/09/2019 10:54, Xuefu Z wrote: > > Hi Dawid, > > Thank you for your summary. While the only difference in the two proposals > is one- or three-part in naming, the consequence would be substantial. > > To me, there are two major use cases of temporary functions compared to > persistent ones: > 1. Temporary in nature and auto managed by the session. More often than > not, admin doesn't even allow user to create persistent functions. > 2. Provide an opportunity to overwriting system built-in functions. > > Since built-in functions has one-part name, requiring three-part name for > temporary functions eliminates the overwriting opportunity. > > One-part naming essentially puts all temp functions under a single > namespace and simplifies function resolution, such as we don't need to > consider the case of a temp function and a persistent function with the > same name under the same database. > > I agree having three-parts does have its merits, such as consistency with > other temporary objects (table) and minor difference between temp vs > catalog functions. However, there is a slight difference between tables and > function in that there is no built-in table in SQL so there is no need to > overwrite it. > > I'm not sure if I fully agree the benefits you listed as the advantages of > the three-part naming of temp functions. > -- Allowing overwriting built-in functions is a benefit and the solution > for disallowing certain overwriting shouldn't be totally banning it. > -- Catalog functions are defined by users, and we suppose they can > drop/alter it in any way they want. Thus, overwriting a catalog function > doesn't seem to be a strong use case that we should be concerned about. > Rather, there are known use case for overwriting built-in functions. > > Thus, personally I would prefer one-part name for temporary functions. In > lack of SQL standard on this, I certainly like to get opinions from others > to see if a consensus can be eventually reached. > > (To your point on modular approach to support external built-in functions, > we saw the value and are actively looking into it. Thanks for sharing your > opinion on that.) > > Thanks, > Xuefu > > On Fri, Sep 6, 2019 at 3:48 PM Dawid Wysakowicz > > wrote: > > > Hi Xuefu, > > Thank you for your answers. > > Let me summarize my understanding. In principle we differ only in regards > to the fact if a temporary function can be only 1-part or only 3-part > identified. I can reconfirm that if the community decides it prefers the > 1-part approach I will commit to that, with the assumption that we will > force ONLY 1-part function names. (We will parse identifier and throw > exception if a user tries to register e.g. db.temp_func). > > My preference is though the 3-part approach: > >- there are some functions that it makes no sense to override, e.g. >CAST, moreover I'm afraid that allowing overriding
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
I agree the consequences of the decision are substantial. Let's see what others think. -- Catalog functions are defined by users, and we suppose they can drop/alter it in any way they want. Thus, overwriting a catalog function doesn't seem to be a strong use case that we should be concerned about. Rather, there are known use case for overwriting built-in functions. Not always users are in full control of the catalog functions. There is also the case where different teams manage the catalog & use the catalog. As for overriding built-in functions with 3-part approach user can always use an equally named function from a catalog. E.g. to override / SELECT explode(arr) FROM .../ user can always write: / SELECT db.explode(arr) FROM .../ Best, Dawid // On 06/09/2019 10:54, Xuefu Z wrote: > Hi Dawid, > > Thank you for your summary. While the only difference in the two proposals > is one- or three-part in naming, the consequence would be substantial. > > To me, there are two major use cases of temporary functions compared to > persistent ones: > 1. Temporary in nature and auto managed by the session. More often than > not, admin doesn't even allow user to create persistent functions. > 2. Provide an opportunity to overwriting system built-in functions. > > Since built-in functions has one-part name, requiring three-part name for > temporary functions eliminates the overwriting opportunity. > > One-part naming essentially puts all temp functions under a single > namespace and simplifies function resolution, such as we don't need to > consider the case of a temp function and a persistent function with the > same name under the same database. > > I agree having three-parts does have its merits, such as consistency with > other temporary objects (table) and minor difference between temp vs > catalog functions. However, there is a slight difference between tables and > function in that there is no built-in table in SQL so there is no need to > overwrite it. > > I'm not sure if I fully agree the benefits you listed as the advantages of > the three-part naming of temp functions. > -- Allowing overwriting built-in functions is a benefit and the solution > for disallowing certain overwriting shouldn't be totally banning it. > -- Catalog functions are defined by users, and we suppose they can > drop/alter it in any way they want. Thus, overwriting a catalog function > doesn't seem to be a strong use case that we should be concerned about. > Rather, there are known use case for overwriting built-in functions. > > Thus, personally I would prefer one-part name for temporary functions. In > lack of SQL standard on this, I certainly like to get opinions from others > to see if a consensus can be eventually reached. > > (To your point on modular approach to support external built-in functions, > we saw the value and are actively looking into it. Thanks for sharing your > opinion on that.) > > Thanks, > Xuefu > > On Fri, Sep 6, 2019 at 3:48 PM Dawid Wysakowicz > wrote: > >> Hi Xuefu, >> >> Thank you for your answers. >> >> Let me summarize my understanding. In principle we differ only in regards >> to the fact if a temporary function can be only 1-part or only 3-part >> identified. I can reconfirm that if the community decides it prefers the >> 1-part approach I will commit to that, with the assumption that we will >> force ONLY 1-part function names. (We will parse identifier and throw >> exception if a user tries to register e.g. db.temp_func). >> >> My preference is though the 3-part approach: >> >>- there are some functions that it makes no sense to override, e.g. >>CAST, moreover I'm afraid that allowing overriding such will lead to high >>inconsistency, similar to those that I mentioned spark has >>- you cannot shadow a fully-qualified function. (If a user fully >>qualifies his/her objects in a SQL query, which is often considered a good >>practice) >>- it does not differentiate between functions & temporary functions. >>Temporary functions just differ with regards to their life-cycle. The >>registration & usage is exactly the same. >> >> As it can be seen, the proposed concept regarding temp function and >> function resolution is quite simple. >> >> Both approaches are equally simple. I would even say the 3-part approach >> is slightly simpler as it does not have to care about some special built-in >> functions such as CAST. >> >> I don't want to express my opinion on the differentiation between built-in >> functions and "external" built-in functions in this thread as it is rather >> orthogonal, but I also like the modular approach and I definitely don't >> like the special syntax "cat::function". I think it's better to stick to a >> standard or at least other proved solutions from other systems. >> >> Best, >> >> Dawid >> On 05/09/2019 10:12, Xuefu Z wrote: >> >> Hi David, >> >> Thanks for sharing your thoughts and request for clarifications. I believe >> that I fully
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Dawid, Thank you for your summary. While the only difference in the two proposals is one- or three-part in naming, the consequence would be substantial. To me, there are two major use cases of temporary functions compared to persistent ones: 1. Temporary in nature and auto managed by the session. More often than not, admin doesn't even allow user to create persistent functions. 2. Provide an opportunity to overwriting system built-in functions. Since built-in functions has one-part name, requiring three-part name for temporary functions eliminates the overwriting opportunity. One-part naming essentially puts all temp functions under a single namespace and simplifies function resolution, such as we don't need to consider the case of a temp function and a persistent function with the same name under the same database. I agree having three-parts does have its merits, such as consistency with other temporary objects (table) and minor difference between temp vs catalog functions. However, there is a slight difference between tables and function in that there is no built-in table in SQL so there is no need to overwrite it. I'm not sure if I fully agree the benefits you listed as the advantages of the three-part naming of temp functions. -- Allowing overwriting built-in functions is a benefit and the solution for disallowing certain overwriting shouldn't be totally banning it. -- Catalog functions are defined by users, and we suppose they can drop/alter it in any way they want. Thus, overwriting a catalog function doesn't seem to be a strong use case that we should be concerned about. Rather, there are known use case for overwriting built-in functions. Thus, personally I would prefer one-part name for temporary functions. In lack of SQL standard on this, I certainly like to get opinions from others to see if a consensus can be eventually reached. (To your point on modular approach to support external built-in functions, we saw the value and are actively looking into it. Thanks for sharing your opinion on that.) Thanks, Xuefu On Fri, Sep 6, 2019 at 3:48 PM Dawid Wysakowicz wrote: > Hi Xuefu, > > Thank you for your answers. > > Let me summarize my understanding. In principle we differ only in regards > to the fact if a temporary function can be only 1-part or only 3-part > identified. I can reconfirm that if the community decides it prefers the > 1-part approach I will commit to that, with the assumption that we will > force ONLY 1-part function names. (We will parse identifier and throw > exception if a user tries to register e.g. db.temp_func). > > My preference is though the 3-part approach: > >- there are some functions that it makes no sense to override, e.g. >CAST, moreover I'm afraid that allowing overriding such will lead to high >inconsistency, similar to those that I mentioned spark has >- you cannot shadow a fully-qualified function. (If a user fully >qualifies his/her objects in a SQL query, which is often considered a good >practice) >- it does not differentiate between functions & temporary functions. >Temporary functions just differ with regards to their life-cycle. The >registration & usage is exactly the same. > > As it can be seen, the proposed concept regarding temp function and > function resolution is quite simple. > > Both approaches are equally simple. I would even say the 3-part approach > is slightly simpler as it does not have to care about some special built-in > functions such as CAST. > > I don't want to express my opinion on the differentiation between built-in > functions and "external" built-in functions in this thread as it is rather > orthogonal, but I also like the modular approach and I definitely don't > like the special syntax "cat::function". I think it's better to stick to a > standard or at least other proved solutions from other systems. > > Best, > > Dawid > On 05/09/2019 10:12, Xuefu Z wrote: > > Hi David, > > Thanks for sharing your thoughts and request for clarifications. I believe > that I fully understood your proposal, which does has its merit. However, > it's different from ours. Here are the answers to your questions: > > Re #1: yes, the temp functions in the proposal are global and have just > one-part names, similar to built-in functions. Two- or three-part names are > not allowed. > > Re #2: not applicable as two- or three-part names are disallowed. > > Re #3: same as above. Referencing external built-in functions is achieved > either implicitly (only the built-in functions in the current catalogs are > considered) or via special syntax such as cat::function. However, we are > looking into the modular approach that Time suggested with other feedback > received from the community. > > Re #4: the resolution order goes like the following in our proposal: > > 1. temporary functions > 2. bulit-in functions (including those augmented by add-on modules) > 3. built-in functions in current catalog (this will not be
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Xuefu, Thank you for your answers. Let me summarize my understanding. In principle we differ only in regards to the fact if a temporary function can be only 1-part or only 3-part identified. I can reconfirm that if the community decides it prefers the 1-part approach I will commit to that, with the assumption that we will force ONLY 1-part function names. (We will parse identifier and throw exception if a user tries to register e.g. db.temp_func). My preference is though the 3-part approach: * there are some functions that it makes no sense to override, e.g. CAST, moreover I'm afraid that allowing overriding such will lead to high inconsistency, similar to those that I mentioned spark has * you cannot shadow a fully-qualified function. (If a user fully qualifies his/her objects in a SQL query, which is often considered a good practice) * it does not differentiate between functions & temporary functions. Temporary functions just differ with regards to their life-cycle. The registration & usage is exactly the same. As it can be seen, the proposed concept regarding temp function and function resolution is quite simple. Both approaches are equally simple. I would even say the 3-part approach is slightly simpler as it does not have to care about some special built-in functions such as CAST. I don't want to express my opinion on the differentiation between built-in functions and "external" built-in functions in this thread as it is rather orthogonal, but I also like the modular approach and I definitely don't like the special syntax "cat::function". I think it's better to stick to a standard or at least other proved solutions from other systems. Best, Dawid On 05/09/2019 10:12, Xuefu Z wrote: > Hi David, > > Thanks for sharing your thoughts and request for clarifications. I believe > that I fully understood your proposal, which does has its merit. However, > it's different from ours. Here are the answers to your questions: > > Re #1: yes, the temp functions in the proposal are global and have just > one-part names, similar to built-in functions. Two- or three-part names are > not allowed. > > Re #2: not applicable as two- or three-part names are disallowed. > > Re #3: same as above. Referencing external built-in functions is achieved > either implicitly (only the built-in functions in the current catalogs are > considered) or via special syntax such as cat::function. However, we are > looking into the modular approach that Time suggested with other feedback > received from the community. > > Re #4: the resolution order goes like the following in our proposal: > > 1. temporary functions > 2. bulit-in functions (including those augmented by add-on modules) > 3. built-in functions in current catalog (this will not be needed if the > special syntax "cat::function" is required) > 4. functions in current catalog and db. > > If we go with the modular approach and make external built-in functions as > an add-on module, the 2 and 3 above will be combined. In essence, the > resolution order is equivalent in the two approaches. > > By the way, resolution order matters only for simple name reference. For > names such as db.function (interpreted as current_cat/db/function) or > cat.db.function, the reference is unambiguous, so on resolution is needed. > > As it can be seen, the proposed concept regarding temp function and > function resolution is quite simple. Additionally, the proposed resolution > order allows temp function to shadow a built-in function, which is > important (though not decisive) in our opinion. > > I started liking the modular approach as the resolution order will only > include 1, 2, and 4, which is simpler and more generic. That's why I > suggested we look more into this direction. > > Please let me know if there are further questions. > > Thanks, > Xuefu > > > > > On Thu, Sep 5, 2019 at 2:42 PM Dawid Wysakowicz > wrote: > >> Hi Xuefu, >> >> Just wanted to summarize my opinion on the one topic (temporary functions). >> >> My preference would be to make temporary functions always 3-part qualified >> (as a result that would prohibit overriding built-in functions). Having >> said that if the community decides that it's better to allow overriding >> built-in functions I am fine with it and can commit to that decision. >> >> I wanted to ask if you could clarify a few points for me around that >> option. >> >>1. Would you enforce temporary functions to be always just a single >>name (without db & cat) as hive does, or would you allow also 3 or even 2 >>part identifiers? >>2. Assuming 2/3-part paths. How would you register a function from a >>following statement: CREATE TEMPORARY FUNCTION db.func? Would that shadow >>all functions named 'func' in all databases named 'db' in all catalogs? Or >>would you shadow only function 'func' in database 'db' in current catalog? >>3. This point is still under discussion, but was mentioned a few
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi David, Thanks for sharing your thoughts and request for clarifications. I believe that I fully understood your proposal, which does has its merit. However, it's different from ours. Here are the answers to your questions: Re #1: yes, the temp functions in the proposal are global and have just one-part names, similar to built-in functions. Two- or three-part names are not allowed. Re #2: not applicable as two- or three-part names are disallowed. Re #3: same as above. Referencing external built-in functions is achieved either implicitly (only the built-in functions in the current catalogs are considered) or via special syntax such as cat::function. However, we are looking into the modular approach that Time suggested with other feedback received from the community. Re #4: the resolution order goes like the following in our proposal: 1. temporary functions 2. bulit-in functions (including those augmented by add-on modules) 3. built-in functions in current catalog (this will not be needed if the special syntax "cat::function" is required) 4. functions in current catalog and db. If we go with the modular approach and make external built-in functions as an add-on module, the 2 and 3 above will be combined. In essence, the resolution order is equivalent in the two approaches. By the way, resolution order matters only for simple name reference. For names such as db.function (interpreted as current_cat/db/function) or cat.db.function, the reference is unambiguous, so on resolution is needed. As it can be seen, the proposed concept regarding temp function and function resolution is quite simple. Additionally, the proposed resolution order allows temp function to shadow a built-in function, which is important (though not decisive) in our opinion. I started liking the modular approach as the resolution order will only include 1, 2, and 4, which is simpler and more generic. That's why I suggested we look more into this direction. Please let me know if there are further questions. Thanks, Xuefu On Thu, Sep 5, 2019 at 2:42 PM Dawid Wysakowicz wrote: > Hi Xuefu, > > Just wanted to summarize my opinion on the one topic (temporary functions). > > My preference would be to make temporary functions always 3-part qualified > (as a result that would prohibit overriding built-in functions). Having > said that if the community decides that it's better to allow overriding > built-in functions I am fine with it and can commit to that decision. > > I wanted to ask if you could clarify a few points for me around that > option. > >1. Would you enforce temporary functions to be always just a single >name (without db & cat) as hive does, or would you allow also 3 or even 2 >part identifiers? >2. Assuming 2/3-part paths. How would you register a function from a >following statement: CREATE TEMPORARY FUNCTION db.func? Would that shadow >all functions named 'func' in all databases named 'db' in all catalogs? Or >would you shadow only function 'func' in database 'db' in current catalog? >3. This point is still under discussion, but was mentioned a few >times, that maybe we want to enable syntax cat.func for "external built-in >functions". How would that affect statement from previous point? Would >'db.func' shadow "external built-in function" in 'db' catalog or user >functions as in point 2? Or maybe both? >4. Lastly in fact to summarize the previous points. Assuming 2/3-part >paths. Would the function resolution be actually as follows?: > 1. temporary functions (1-part path) > 2. built-in functions > 3. temporary functions (2-part path) > 4. 2-part catalog functions a.k.a. "external built-in functions" > (cat + func) - this is still under discussion, if we want that in the > other > focal point > 5. temporary functions (3-part path) > 6. 3-part catalog functions a.k.a. user functions > > I would be really grateful if you could explain me those questions, thanks. > > BTW, Thank you all for a healthy discussion. > > Best, > > Dawid > On 04/09/2019 23:25, Xuefu Z wrote: > > Thank all for the sharing thoughts. I think we have gathered some useful > initial feedback from this long discussion with a couple of focal points > sticking out. > > We will go back to do more research and adapt our proposal. Once it's > ready, we will ask for a new round of review. If there is any disagreement, > we will start a new discussion thread on each rather than having a mega > discussion like this. > > Thanks to everyone for participating. > > Regards, > Xuefu > > > On Thu, Sep 5, 2019 at 2:52 AM Bowen Li > wrote: > > > Let me try to summarize and conclude the long thread so far: > > 1. For order of temp function v.s. built-in function: > > I think Dawid's point that temp function should be of fully qualified path > is a better reasoning to back the newly proposed order, and i agree we > don't need to follow Hive/Spark. > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Xuefu, Just wanted to summarize my opinion on the one topic (temporary functions). My preference would be to make temporary functions always 3-part qualified (as a result that would prohibit overriding built-in functions). Having said that if the community decides that it's better to allow overriding built-in functions I am fine with it and can commit to that decision. I wanted to ask if you could clarify a few points for me around that option. 1. Would you enforce temporary functions to be always just a single name (without db & cat) as hive does, or would you allow also 3 or even 2 part identifiers? 2. Assuming 2/3-part paths. How would you register a function from a following statement: CREATE TEMPORARY FUNCTION db.func? Would that shadow all functions named 'func' in all databases named 'db' in all catalogs? Or would you shadow only function 'func' in database 'db' in current catalog? 3. This point is still under discussion, but was mentioned a few times, that maybe we want to enable syntax cat.func for "external built-in functions". How would that affect statement from previous point? Would 'db.func' shadow "external built-in function" in 'db' catalog or user functions as in point 2? Or maybe both? 4. Lastly in fact to summarize the previous points. Assuming 2/3-part paths. Would the function resolution be actually as follows?: 1. temporary functions (1-part path) 2. built-in functions 3. temporary functions (2-part path) 4. 2-part catalog functions a.k.a. "external built-in functions" (cat + func) - this is still under discussion, if we want that in the other focal point 5. temporary functions (3-part path) 6. 3-part catalog functions a.k.a. user functions I would be really grateful if you could explain me those questions, thanks. BTW, Thank you all for a healthy discussion. Best, Dawid On 04/09/2019 23:25, Xuefu Z wrote: > Thank all for the sharing thoughts. I think we have gathered some useful > initial feedback from this long discussion with a couple of focal points > sticking out. > > We will go back to do more research and adapt our proposal. Once it's > ready, we will ask for a new round of review. If there is any disagreement, > we will start a new discussion thread on each rather than having a mega > discussion like this. > > Thanks to everyone for participating. > > Regards, > Xuefu > > > On Thu, Sep 5, 2019 at 2:52 AM Bowen Li wrote: > >> Let me try to summarize and conclude the long thread so far: >> >> 1. For order of temp function v.s. built-in function: >> >> I think Dawid's point that temp function should be of fully qualified path >> is a better reasoning to back the newly proposed order, and i agree we >> don't need to follow Hive/Spark. >> >> However, I'd rather not change fundamentals of temporary functions in this >> FLIP. It belongs to a bigger story of how temporary objects should be >> redefined and be handled uniformly - currently temporary tables and views >> (those registered from TableEnv#registerTable()) behave different than what >> Dawid propose for temp functions, and we need a FLIP to just unify their >> APIs and behaviors. >> >> I agree that backward compatibility is not an issue w.r.t Jark's points. >> >> ***Seems we do have consensus that it's acceptable to prevent users >> registering a temp function in the same name as a built-in function. To >> help us move forward, I'd like to propose setting such a restraint on temp >> functions in this FLIP to simplify the design and avoid disputes.*** It >> will also leave rooms for improvements in the future. >> >> >> 2. For Hive built-in function: >> >> Thanks Timo for providing the Presto and Postgres examples. I feel modular >> built-in functions can be a good fit for the geo and ml example as a native >> Flink extension, but not sure if it fits well with external integrations. >> Anyway, I think modular built-in functions is a bigger story and can be on >> its own thread too, and our proposal doesn't prevent Flink from doing that >> in the future. >> >> ***Seems we have consensus that users should be able to use built-in >> functions of Hive or other external systems in SQL explicitly and >> deterministically regardless of Flink built-in functions and the potential >> modular built-in functions, via some new syntax like "mycat::func"? If so, >> I'd like to propose removing Hive built-in functions from ambiguous >> function resolution order, and empower users with such a syntax. This way >> we sacrifice a little convenience for certainty*** >> >> >> What do you think? >> >> On Wed, Sep 4, 2019 at 7:02 AM Dawid Wysakowicz >> wrote: >> >>> Hi, >>> >>> Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just >>> performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they >> are >>> very inconsistent in that manner (spark being way worse on that). >>> >>> Hive: >>> >>> You cannot overwrite all
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Maybe Xuefu missed my email. Please let me know what your thoughts are on the summary, if there's still major controversy, I can take time to reevaluate that part. On Wed, Sep 4, 2019 at 2:25 PM Xuefu Z wrote: > Thank all for the sharing thoughts. I think we have gathered some useful > initial feedback from this long discussion with a couple of focal points > sticking out. > > We will go back to do more research and adapt our proposal. Once it's > ready, we will ask for a new round of review. If there is any disagreement, > we will start a new discussion thread on each rather than having a mega > discussion like this. > > Thanks to everyone for participating. > > Regards, > Xuefu > > > On Thu, Sep 5, 2019 at 2:52 AM Bowen Li wrote: > > > Let me try to summarize and conclude the long thread so far: > > > > 1. For order of temp function v.s. built-in function: > > > > I think Dawid's point that temp function should be of fully qualified > path > > is a better reasoning to back the newly proposed order, and i agree we > > don't need to follow Hive/Spark. > > > > However, I'd rather not change fundamentals of temporary functions in > this > > FLIP. It belongs to a bigger story of how temporary objects should be > > redefined and be handled uniformly - currently temporary tables and views > > (those registered from TableEnv#registerTable()) behave different than > what > > Dawid propose for temp functions, and we need a FLIP to just unify their > > APIs and behaviors. > > > > I agree that backward compatibility is not an issue w.r.t Jark's points. > > > > ***Seems we do have consensus that it's acceptable to prevent users > > registering a temp function in the same name as a built-in function. To > > help us move forward, I'd like to propose setting such a restraint on > temp > > functions in this FLIP to simplify the design and avoid disputes.*** It > > will also leave rooms for improvements in the future. > > > > > > 2. For Hive built-in function: > > > > Thanks Timo for providing the Presto and Postgres examples. I feel > modular > > built-in functions can be a good fit for the geo and ml example as a > native > > Flink extension, but not sure if it fits well with external integrations. > > Anyway, I think modular built-in functions is a bigger story and can be > on > > its own thread too, and our proposal doesn't prevent Flink from doing > that > > in the future. > > > > ***Seems we have consensus that users should be able to use built-in > > functions of Hive or other external systems in SQL explicitly and > > deterministically regardless of Flink built-in functions and the > potential > > modular built-in functions, via some new syntax like "mycat::func"? If > so, > > I'd like to propose removing Hive built-in functions from ambiguous > > function resolution order, and empower users with such a syntax. This way > > we sacrifice a little convenience for certainty*** > > > > > > What do you think? > > > > On Wed, Sep 4, 2019 at 7:02 AM Dawid Wysakowicz > > wrote: > > > > > Hi, > > > > > > Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just > > > performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they > > are > > > very inconsistent in that manner (spark being way worse on that). > > > > > > Hive: > > > > > > You cannot overwrite all the built-in functions. I could overwrite most > > of > > > the functions I tried e.g. length, e, pi, round, rtrim, but there are > > > functions I cannot overwrite e.g. CAST, ARRAY I get: > > > > > > > > > *ParseException line 1:29 cannot recognize input near 'array' 'AS' > * > > > > > > What is interesting is that I cannot ovewrite *array*, but I can > ovewrite > > > *map* or *struct*. Though hive behaves reasonable well if I manage to > > > overwrite a function. When I drop the temporary function the native > > > function is still available. > > > > > > Spark: > > > > > > Spark's behavior imho is super bad. > > > > > > Theoretically I could overwrite all functions. I was able e.g. to > > > overwrite CAST function. I had to use though CREATE OR REPLACE > TEMPORARY > > > FUNCTION syntax. Otherwise I get an exception that a function already > > > exists. However when I used the CAST function in a query it used the > > > native, built-in one. > > > > > > When I overwrote current_date() function, it was used in a query, but > it > > > completely replaces the built-in function and I can no longer use the > > > native function in any way. I cannot also drop the temporary function. > I > > > get: > > > > > > *Error in query: Cannot drop native function 'current_date';* > > > > > > Additional note, both systems do not allow creating TEMPORARY FUNCTIONS > > > with a database. Temporary functions are always represented as a single > > > name. > > > > > > In my opinion neither of the systems have consistent behavior. > Generally > > > speaking I think overwriting any system provided functions is just > > > dangerous. > > > > > > Regarding
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thank all for the sharing thoughts. I think we have gathered some useful initial feedback from this long discussion with a couple of focal points sticking out. We will go back to do more research and adapt our proposal. Once it's ready, we will ask for a new round of review. If there is any disagreement, we will start a new discussion thread on each rather than having a mega discussion like this. Thanks to everyone for participating. Regards, Xuefu On Thu, Sep 5, 2019 at 2:52 AM Bowen Li wrote: > Let me try to summarize and conclude the long thread so far: > > 1. For order of temp function v.s. built-in function: > > I think Dawid's point that temp function should be of fully qualified path > is a better reasoning to back the newly proposed order, and i agree we > don't need to follow Hive/Spark. > > However, I'd rather not change fundamentals of temporary functions in this > FLIP. It belongs to a bigger story of how temporary objects should be > redefined and be handled uniformly - currently temporary tables and views > (those registered from TableEnv#registerTable()) behave different than what > Dawid propose for temp functions, and we need a FLIP to just unify their > APIs and behaviors. > > I agree that backward compatibility is not an issue w.r.t Jark's points. > > ***Seems we do have consensus that it's acceptable to prevent users > registering a temp function in the same name as a built-in function. To > help us move forward, I'd like to propose setting such a restraint on temp > functions in this FLIP to simplify the design and avoid disputes.*** It > will also leave rooms for improvements in the future. > > > 2. For Hive built-in function: > > Thanks Timo for providing the Presto and Postgres examples. I feel modular > built-in functions can be a good fit for the geo and ml example as a native > Flink extension, but not sure if it fits well with external integrations. > Anyway, I think modular built-in functions is a bigger story and can be on > its own thread too, and our proposal doesn't prevent Flink from doing that > in the future. > > ***Seems we have consensus that users should be able to use built-in > functions of Hive or other external systems in SQL explicitly and > deterministically regardless of Flink built-in functions and the potential > modular built-in functions, via some new syntax like "mycat::func"? If so, > I'd like to propose removing Hive built-in functions from ambiguous > function resolution order, and empower users with such a syntax. This way > we sacrifice a little convenience for certainty*** > > > What do you think? > > On Wed, Sep 4, 2019 at 7:02 AM Dawid Wysakowicz > wrote: > > > Hi, > > > > Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just > > performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they > are > > very inconsistent in that manner (spark being way worse on that). > > > > Hive: > > > > You cannot overwrite all the built-in functions. I could overwrite most > of > > the functions I tried e.g. length, e, pi, round, rtrim, but there are > > functions I cannot overwrite e.g. CAST, ARRAY I get: > > > > > > *ParseException line 1:29 cannot recognize input near 'array' 'AS' * > > > > What is interesting is that I cannot ovewrite *array*, but I can ovewrite > > *map* or *struct*. Though hive behaves reasonable well if I manage to > > overwrite a function. When I drop the temporary function the native > > function is still available. > > > > Spark: > > > > Spark's behavior imho is super bad. > > > > Theoretically I could overwrite all functions. I was able e.g. to > > overwrite CAST function. I had to use though CREATE OR REPLACE TEMPORARY > > FUNCTION syntax. Otherwise I get an exception that a function already > > exists. However when I used the CAST function in a query it used the > > native, built-in one. > > > > When I overwrote current_date() function, it was used in a query, but it > > completely replaces the built-in function and I can no longer use the > > native function in any way. I cannot also drop the temporary function. I > > get: > > > > *Error in query: Cannot drop native function 'current_date';* > > > > Additional note, both systems do not allow creating TEMPORARY FUNCTIONS > > with a database. Temporary functions are always represented as a single > > name. > > > > In my opinion neither of the systems have consistent behavior. Generally > > speaking I think overwriting any system provided functions is just > > dangerous. > > > > Regarding Jark's concerns. Such functions would be registered in a > current > > catalog/database schema, so a user could still use its own function, but > > would have to fully qualify the function (because built-in functions take > > precedence). Moreover users would have the same problem with permanent > > functions. Imagine a user have a permanent function 'cat.db.explode'. In > > 1.9 the user could use just the 'explode' function as long as the 'cat' & > > 'db' were
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi David, Thanks for sharing the findings about temporary functions. Because of strong inconsistency observed in Spark, we can probably ignore it for now. For Hive, I understand one may not be able to overwrite everything, but the capability is being offered. Whether we offer this capability is to be determined, I don't see the "danger" you mentioned. It's user's action, which only impacts the user's current session. Other users are not impacted. (That's one of the benefits of temporary objects.) We cannot always prevent users from making mistakes. If we think overwriting is useful to the user, then we can allow it. To make it more consistent, we can also further restrict by further blacklisting built-in functions that may not be overwritten. In my past experience, I did see user needs to overwriting a built-in function in Hive. Without this capability, user has to create a permanent function and modify all the queries referencing the function with it fully-qualified name. This is equivalent to create a new, user-defined, function. This way can work, but the usability is bad. (Jark's "explode" example is actually important because forcing user to modify query is of bad experience after an upgrade.) In short, we can theoretically disallow function overwriting since there is no standard. However, I don't see strong reasons for doing so, especially such a capability is useful to some users. Thanks, Xuefu On Wed, Sep 4, 2019 at 10:02 PM Dawid Wysakowicz wrote: > Hi, > > Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just > performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they are > very inconsistent in that manner (spark being way worse on that). > > Hive: > > You cannot overwrite all the built-in functions. I could overwrite most of > the functions I tried e.g. length, e, pi, round, rtrim, but there are > functions I cannot overwrite e.g. CAST, ARRAY I get: > > > *ParseException line 1:29 cannot recognize input near 'array' 'AS' * > > What is interesting is that I cannot ovewrite *array*, but I can ovewrite > *map* or *struct*. Though hive behaves reasonable well if I manage to > overwrite a function. When I drop the temporary function the native > function is still available. > > Spark: > > Spark's behavior imho is super bad. > > Theoretically I could overwrite all functions. I was able e.g. to > overwrite CAST function. I had to use though CREATE OR REPLACE TEMPORARY > FUNCTION syntax. Otherwise I get an exception that a function already > exists. However when I used the CAST function in a query it used the > native, built-in one. > > When I overwrote current_date() function, it was used in a query, but it > completely replaces the built-in function and I can no longer use the > native function in any way. I cannot also drop the temporary function. I > get: > > *Error in query: Cannot drop native function 'current_date';* > > Additional note, both systems do not allow creating TEMPORARY FUNCTIONS > with a database. Temporary functions are always represented as a single > name. > > In my opinion neither of the systems have consistent behavior. Generally > speaking I think overwriting any system provided functions is just > dangerous. > > Regarding Jark's concerns. Such functions would be registered in a current > catalog/database schema, so a user could still use its own function, but > would have to fully qualify the function (because built-in functions take > precedence). Moreover users would have the same problem with permanent > functions. Imagine a user have a permanent function 'cat.db.explode'. In > 1.9 the user could use just the 'explode' function as long as the 'cat' & > 'db' were the default catalog & database. If we introduce 'explode' > built-in function in 1.10, the user has to fully qualify the function. > > Best, > > Dawid > On 04/09/2019 15:19, Timo Walther wrote: > > Hi all, > > thanks for the healthy discussion. It is already a very long discussion > with a lot of text. So I will just post my opinion to a couple of > statements: > > > Hive built-in functions are not part of Flink built-in functions, they > are catalog functions > > That is not entirely true. Correct me if I'm wrong but I think Hive > built-in functions are also not catalog functions. They are not stored in > every Hive metastore catalog that is freshly created but are a set of > functions that are listed somewhere and made available. > > > ambiguous functions reference just shouldn't be resolved to a different > catalog > > I agree. They should not be resolved to a different catalog. That's why I > am suggesting to split the concept of built-in functions and catalog lookup > semantics. > > > I don't know if any other databases handle built-in functions like that > > What I called "module" is: > - Extension in Postgres [1] > - Plugin in Presto [2] > > Btw. Presto even mentions example modules that are similar to the ones > that we will introduce in the near future
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Let me try to summarize and conclude the long thread so far: 1. For order of temp function v.s. built-in function: I think Dawid's point that temp function should be of fully qualified path is a better reasoning to back the newly proposed order, and i agree we don't need to follow Hive/Spark. However, I'd rather not change fundamentals of temporary functions in this FLIP. It belongs to a bigger story of how temporary objects should be redefined and be handled uniformly - currently temporary tables and views (those registered from TableEnv#registerTable()) behave different than what Dawid propose for temp functions, and we need a FLIP to just unify their APIs and behaviors. I agree that backward compatibility is not an issue w.r.t Jark's points. ***Seems we do have consensus that it's acceptable to prevent users registering a temp function in the same name as a built-in function. To help us move forward, I'd like to propose setting such a restraint on temp functions in this FLIP to simplify the design and avoid disputes.*** It will also leave rooms for improvements in the future. 2. For Hive built-in function: Thanks Timo for providing the Presto and Postgres examples. I feel modular built-in functions can be a good fit for the geo and ml example as a native Flink extension, but not sure if it fits well with external integrations. Anyway, I think modular built-in functions is a bigger story and can be on its own thread too, and our proposal doesn't prevent Flink from doing that in the future. ***Seems we have consensus that users should be able to use built-in functions of Hive or other external systems in SQL explicitly and deterministically regardless of Flink built-in functions and the potential modular built-in functions, via some new syntax like "mycat::func"? If so, I'd like to propose removing Hive built-in functions from ambiguous function resolution order, and empower users with such a syntax. This way we sacrifice a little convenience for certainty*** What do you think? On Wed, Sep 4, 2019 at 7:02 AM Dawid Wysakowicz wrote: > Hi, > > Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just > performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they are > very inconsistent in that manner (spark being way worse on that). > > Hive: > > You cannot overwrite all the built-in functions. I could overwrite most of > the functions I tried e.g. length, e, pi, round, rtrim, but there are > functions I cannot overwrite e.g. CAST, ARRAY I get: > > > *ParseException line 1:29 cannot recognize input near 'array' 'AS' * > > What is interesting is that I cannot ovewrite *array*, but I can ovewrite > *map* or *struct*. Though hive behaves reasonable well if I manage to > overwrite a function. When I drop the temporary function the native > function is still available. > > Spark: > > Spark's behavior imho is super bad. > > Theoretically I could overwrite all functions. I was able e.g. to > overwrite CAST function. I had to use though CREATE OR REPLACE TEMPORARY > FUNCTION syntax. Otherwise I get an exception that a function already > exists. However when I used the CAST function in a query it used the > native, built-in one. > > When I overwrote current_date() function, it was used in a query, but it > completely replaces the built-in function and I can no longer use the > native function in any way. I cannot also drop the temporary function. I > get: > > *Error in query: Cannot drop native function 'current_date';* > > Additional note, both systems do not allow creating TEMPORARY FUNCTIONS > with a database. Temporary functions are always represented as a single > name. > > In my opinion neither of the systems have consistent behavior. Generally > speaking I think overwriting any system provided functions is just > dangerous. > > Regarding Jark's concerns. Such functions would be registered in a current > catalog/database schema, so a user could still use its own function, but > would have to fully qualify the function (because built-in functions take > precedence). Moreover users would have the same problem with permanent > functions. Imagine a user have a permanent function 'cat.db.explode'. In > 1.9 the user could use just the 'explode' function as long as the 'cat' & > 'db' were the default catalog & database. If we introduce 'explode' > built-in function in 1.10, the user has to fully qualify the function. > > Best, > > Dawid > On 04/09/2019 15:19, Timo Walther wrote: > > Hi all, > > thanks for the healthy discussion. It is already a very long discussion > with a lot of text. So I will just post my opinion to a couple of > statements: > > > Hive built-in functions are not part of Flink built-in functions, they > are catalog functions > > That is not entirely true. Correct me if I'm wrong but I think Hive > built-in functions are also not catalog functions. They are not stored in > every Hive metastore catalog that is freshly created but are a set of > functions
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, Regarding the Hive & Spark support of TEMPORARY FUNCTIONS. I've just performed some experiments (hive-2.3.2 & spark 2.4.4) and I think they are very inconsistent in that manner (spark being way worse on that). Hive: You cannot overwrite all the built-in functions. I could overwrite most of the functions I tried e.g. length, e, pi, round, rtrim, but there are functions I cannot overwrite e.g. CAST, ARRAY I get: / ParseException line 1:29 cannot recognize input near 'array' 'AS' / What is interesting is that I cannot ovewrite /array/, but I can ovewrite /map/ or /struct/. Though hive behaves reasonable well if I manage to overwrite a function. When I drop the temporary function the native function is still available. Spark: Spark's behavior imho is super bad. Theoretically I could overwrite all functions. I was able e.g. to overwrite CAST function. I had to use though CREATE OR REPLACE TEMPORARY FUNCTION syntax. Otherwise I get an exception that a function already exists. However when I used the CAST function in a query it used the native, built-in one. When I overwrote current_date() function, it was used in a query, but it completely replaces the built-in function and I can no longer use the native function in any way. I cannot also drop the temporary function. I get: / Error in query: Cannot drop native function 'current_date';/ Additional note, both systems do not allow creating TEMPORARY FUNCTIONS with a database. Temporary functions are always represented as a single name. In my opinion neither of the systems have consistent behavior. Generally speaking I think overwriting any system provided functions is just dangerous. Regarding Jark's concerns. Such functions would be registered in a current catalog/database schema, so a user could still use its own function, but would have to fully qualify the function (because built-in functions take precedence). Moreover users would have the same problem with permanent functions. Imagine a user have a permanent function 'cat.db.explode'. In 1.9 the user could use just the 'explode' function as long as the 'cat' & 'db' were the default catalog & database. If we introduce 'explode' built-in function in 1.10, the user has to fully qualify the function. Best, Dawid On 04/09/2019 15:19, Timo Walther wrote: > Hi all, > > thanks for the healthy discussion. It is already a very long > discussion with a lot of text. So I will just post my opinion to a > couple of statements: > > > Hive built-in functions are not part of Flink built-in functions, > they are catalog functions > > That is not entirely true. Correct me if I'm wrong but I think Hive > built-in functions are also not catalog functions. They are not stored > in every Hive metastore catalog that is freshly created but are a set > of functions that are listed somewhere and made available. > > > ambiguous functions reference just shouldn't be resolved to a > different catalog > > I agree. They should not be resolved to a different catalog. That's > why I am suggesting to split the concept of built-in functions and > catalog lookup semantics. > > > I don't know if any other databases handle built-in functions like that > > What I called "module" is: > - Extension in Postgres [1] > - Plugin in Presto [2] > > Btw. Presto even mentions example modules that are similar to the ones > that we will introduce in the near future both for ML and System XYZ > compatibility: > "See either the presto-ml module for machine learning functions or the > presto-teradata-functions module for Teradata-compatible functions, > both in the root of the Presto source." > > > functions should be either built-in already or just libraries > functions, and library functions can be adapted to catalog APIs or of > some other syntax to use > > Regarding "built-in already", of course we can add a lot of functions > as built-ins but we will end-up in a dependency hell in the near > future if we don't introduce a pluggable approach. Library functions > is what you also suggest but storing them in a catalog means to always > fully qualify them or modifying the existing catalog design that was > inspired by the standard. > > I don't think "it brings in even more complicated scenarios to the > design", it just does clear separation of concerns. Integrating the > functionality into the current design makes the catalog API more > complicated. > > > why would users name a temporary function the same as a built-in > function then? > > Because you never know what users do. If they don't, my suggested > resolution order should not be a problem, right? > > > I don't think hive functions deserves be a function module > > Our goal is not to create a Hive clone. We need to think forward and > Hive is just one of many systems that we can support. Not every > built-in function behaves and will behave exactly like Hive. > > > regarding temporary functions, there are few systems that support it > > IMHO Spark and Hive are not always the
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all, thanks for the healthy discussion. It is already a very long discussion with a lot of text. So I will just post my opinion to a couple of statements: > Hive built-in functions are not part of Flink built-in functions, they are catalog functions That is not entirely true. Correct me if I'm wrong but I think Hive built-in functions are also not catalog functions. They are not stored in every Hive metastore catalog that is freshly created but are a set of functions that are listed somewhere and made available. > ambiguous functions reference just shouldn't be resolved to a different catalog I agree. They should not be resolved to a different catalog. That's why I am suggesting to split the concept of built-in functions and catalog lookup semantics. > I don't know if any other databases handle built-in functions like that What I called "module" is: - Extension in Postgres [1] - Plugin in Presto [2] Btw. Presto even mentions example modules that are similar to the ones that we will introduce in the near future both for ML and System XYZ compatibility: "See either the presto-ml module for machine learning functions or the presto-teradata-functions module for Teradata-compatible functions, both in the root of the Presto source." > functions should be either built-in already or just libraries functions, and library functions can be adapted to catalog APIs or of some other syntax to use Regarding "built-in already", of course we can add a lot of functions as built-ins but we will end-up in a dependency hell in the near future if we don't introduce a pluggable approach. Library functions is what you also suggest but storing them in a catalog means to always fully qualify them or modifying the existing catalog design that was inspired by the standard. I don't think "it brings in even more complicated scenarios to the design", it just does clear separation of concerns. Integrating the functionality into the current design makes the catalog API more complicated. > why would users name a temporary function the same as a built-in function then? Because you never know what users do. If they don't, my suggested resolution order should not be a problem, right? > I don't think hive functions deserves be a function module Our goal is not to create a Hive clone. We need to think forward and Hive is just one of many systems that we can support. Not every built-in function behaves and will behave exactly like Hive. > regarding temporary functions, there are few systems that support it IMHO Spark and Hive are not always the best examples for consistent design. Systems like Postgres, Presto, or SQL Server should be used as a reference. I don't think that a user can overwrite a built-in function there. Regards, Timo [1] https://www.postgresql.org/docs/10/extend-extensions.html [2] https://prestodb.github.io/docs/current/develop/functions.html On 04.09.19 13:44, Jark Wu wrote: Hi all, Regarding #1 temp function <> built-in function and naming. I'm fine with temp functions should precede built-in function and can override built-in functions (we already support to override built-in function in 1.9). If we don't allow the same name as a built-in function, I'm afraid we will have compatibility issues in the future. Say users register a user defined function named "explode" in 1.9, and we support a built-in "explode" function in 1.10. Then the user's jobs which call the registered "explode" function in 1.9 will all fail in 1.10 because of naming conflict. Regarding #2 "External" built-in functions. I think if we store external built-in functions in catalog, then "hive1::sqrt" is a good way to go. However, I would prefer to support a discovery mechanism (e.g. SPI) for built-in functions as Timo suggested above. This gives us the flexibility to add Hive or MySQL or Geo or whatever function set as built-in functions in an easy way. Best, Jark On Wed, 4 Sep 2019 at 17:47, Xuefu Z wrote: Hi David, Thank you for sharing your findings. It seems to me that there is no SQL standard regarding temporary functions. There are few systems that support it. Here are what I have found: 1. Hive: no DB qualifier allowed. Can overwrite built-in. 2. Spark: basically follows Hive ( https://docs.databricks.com/spark/latest/spark-sql/language-manual/create-function.html ) 3. SAP SQL Anywhere Server: can have owner (db?). Not sure of overwriting behavior. ( http://dcx.sap.com/sqla170/en/html/816bdf316ce210148d3acbebf6d39b18.html) Because of lack of standard, it's perfectly fine for Flink to define whatever it sees appropriate. Thus, your proposal (no overwriting and must have DB as holder) is one option. The advantage is simplicity, The downside is the deviation from Hive, which is popular and de facto standard in big data world. However, I don't think we have to follow Hive. More importantly, we need a consensus. I have no objection if your proposal is generally agreed upon.
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all, Regarding #1 temp function <> built-in function and naming. I'm fine with temp functions should precede built-in function and can override built-in functions (we already support to override built-in function in 1.9). If we don't allow the same name as a built-in function, I'm afraid we will have compatibility issues in the future. Say users register a user defined function named "explode" in 1.9, and we support a built-in "explode" function in 1.10. Then the user's jobs which call the registered "explode" function in 1.9 will all fail in 1.10 because of naming conflict. Regarding #2 "External" built-in functions. I think if we store external built-in functions in catalog, then "hive1::sqrt" is a good way to go. However, I would prefer to support a discovery mechanism (e.g. SPI) for built-in functions as Timo suggested above. This gives us the flexibility to add Hive or MySQL or Geo or whatever function set as built-in functions in an easy way. Best, Jark On Wed, 4 Sep 2019 at 17:47, Xuefu Z wrote: > Hi David, > > Thank you for sharing your findings. It seems to me that there is no SQL > standard regarding temporary functions. There are few systems that support > it. Here are what I have found: > > 1. Hive: no DB qualifier allowed. Can overwrite built-in. > 2. Spark: basically follows Hive ( > > https://docs.databricks.com/spark/latest/spark-sql/language-manual/create-function.html > ) > 3. SAP SQL Anywhere Server: can have owner (db?). Not sure of overwriting > behavior. ( > http://dcx.sap.com/sqla170/en/html/816bdf316ce210148d3acbebf6d39b18.html) > > Because of lack of standard, it's perfectly fine for Flink to define > whatever it sees appropriate. Thus, your proposal (no overwriting and must > have DB as holder) is one option. The advantage is simplicity, The downside > is the deviation from Hive, which is popular and de facto standard in big > data world. > > However, I don't think we have to follow Hive. More importantly, we need a > consensus. I have no objection if your proposal is generally agreed upon. > > Thanks, > Xuefu > > On Tue, Sep 3, 2019 at 11:58 PM Dawid Wysakowicz > wrote: > > > Hi all, > > > > Just an opinion on the built-in <> temporary functions resolution and > > NAMING issue. I think we should not allow overriding the built-in > > functions, as this may pose serious issues and to be honest is rather > > not feasible and would require major rework. What happens if a user > > wants to override CAST? Calls to that function are generated at > > different layers of the stack that unfortunately does not always go > > through the Catalog API (at least yet). Moreover from what I've checked > > no other systems allow overriding the built-in functions. All the > > systems I've checked so far register temporary functions in a > > database/schema (either special database for temporary functions, or > > just current database). What I would suggest is to always register > > temporary functions with a 3 part identifier. The same way as tables, > > views etc. This effectively means you cannot override built-in > > functions. With such approach it is natural that the temporary functions > > end up a step lower in the resolution order: > > > > 1. built-in functions (1 part, maybe 2? - this is still under discussion) > > > > 2. temporary functions (always 3 part path) > > > > 3. catalog functions (always 3 part path) > > > > Let me know what do you think. > > > > Best, > > > > Dawid > > > > On 04/09/2019 06:13, Bowen Li wrote: > > > Hi, > > > > > > I agree with Xuefu that the main controversial points are mainly the > two > > > places. My thoughts on them: > > > > > > 1) Determinism of referencing Hive built-in functions. We can either > > remove > > > Hive built-in functions from ambiguous function resolution and require > > > users to use special syntax for their qualified names, or add a config > > flag > > > to catalog constructor/yaml for turning on and off Hive built-in > > functions > > > with the flag set to 'false' by default and proper doc added to help > > users > > > make their decisions. > > > > > > 2) Flink temp functions v.s. Flink built-in functions in ambiguous > > function > > > resolution order. We believe Flink temp functions should precede Flink > > > built-in functions, and I have presented my reasons. Just in case if we > > > cannot reach an agreement, I propose forbid users registering temp > > > functions in the same name as a built-in function, like MySQL's > approach, > > > for the moment. It won't have any performance concern, since built-in > > > functions are all in memory and thus cost of a name check will be > really > > > trivial. > > > > > > > > > On Tue, Sep 3, 2019 at 8:01 PM Xuefu Z wrote: > > > > > >> From what I have seen, there are a couple of focal disagreements: > > >> > > >> 1. Resolution order: temp function --> flink built-in function --> > > catalog > > >> function vs flink built-in function --> temp function -> catalog > > function. > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi David, Thank you for sharing your findings. It seems to me that there is no SQL standard regarding temporary functions. There are few systems that support it. Here are what I have found: 1. Hive: no DB qualifier allowed. Can overwrite built-in. 2. Spark: basically follows Hive ( https://docs.databricks.com/spark/latest/spark-sql/language-manual/create-function.html ) 3. SAP SQL Anywhere Server: can have owner (db?). Not sure of overwriting behavior. ( http://dcx.sap.com/sqla170/en/html/816bdf316ce210148d3acbebf6d39b18.html) Because of lack of standard, it's perfectly fine for Flink to define whatever it sees appropriate. Thus, your proposal (no overwriting and must have DB as holder) is one option. The advantage is simplicity, The downside is the deviation from Hive, which is popular and de facto standard in big data world. However, I don't think we have to follow Hive. More importantly, we need a consensus. I have no objection if your proposal is generally agreed upon. Thanks, Xuefu On Tue, Sep 3, 2019 at 11:58 PM Dawid Wysakowicz wrote: > Hi all, > > Just an opinion on the built-in <> temporary functions resolution and > NAMING issue. I think we should not allow overriding the built-in > functions, as this may pose serious issues and to be honest is rather > not feasible and would require major rework. What happens if a user > wants to override CAST? Calls to that function are generated at > different layers of the stack that unfortunately does not always go > through the Catalog API (at least yet). Moreover from what I've checked > no other systems allow overriding the built-in functions. All the > systems I've checked so far register temporary functions in a > database/schema (either special database for temporary functions, or > just current database). What I would suggest is to always register > temporary functions with a 3 part identifier. The same way as tables, > views etc. This effectively means you cannot override built-in > functions. With such approach it is natural that the temporary functions > end up a step lower in the resolution order: > > 1. built-in functions (1 part, maybe 2? - this is still under discussion) > > 2. temporary functions (always 3 part path) > > 3. catalog functions (always 3 part path) > > Let me know what do you think. > > Best, > > Dawid > > On 04/09/2019 06:13, Bowen Li wrote: > > Hi, > > > > I agree with Xuefu that the main controversial points are mainly the two > > places. My thoughts on them: > > > > 1) Determinism of referencing Hive built-in functions. We can either > remove > > Hive built-in functions from ambiguous function resolution and require > > users to use special syntax for their qualified names, or add a config > flag > > to catalog constructor/yaml for turning on and off Hive built-in > functions > > with the flag set to 'false' by default and proper doc added to help > users > > make their decisions. > > > > 2) Flink temp functions v.s. Flink built-in functions in ambiguous > function > > resolution order. We believe Flink temp functions should precede Flink > > built-in functions, and I have presented my reasons. Just in case if we > > cannot reach an agreement, I propose forbid users registering temp > > functions in the same name as a built-in function, like MySQL's approach, > > for the moment. It won't have any performance concern, since built-in > > functions are all in memory and thus cost of a name check will be really > > trivial. > > > > > > On Tue, Sep 3, 2019 at 8:01 PM Xuefu Z wrote: > > > >> From what I have seen, there are a couple of focal disagreements: > >> > >> 1. Resolution order: temp function --> flink built-in function --> > catalog > >> function vs flink built-in function --> temp function -> catalog > function. > >> 2. "External" built-in functions: how to treat built-in functions in > >> external system and how users reference them > >> > >> For #1, I agree with Bowen that temp function needs to be at the highest > >> priority because that's how a user might overwrite a built-in function > >> without referencing a persistent, overwriting catalog function with a > fully > >> qualified name. Putting built-in functions at the highest priority > >> eliminates that usage. > >> > >> For #2, I saw a general agreement on referencing "external" built-in > >> functions such as those in Hive needs to be explicit and deterministic > even > >> though different approaches are proposed. To limit the scope and simply > the > >> usage, it seems making sense to me to introduce special syntax for > user to > >> explicitly reference an external built-in function such as hive1::sqrt > or > >> hive1._built_in.sqrt. This is a DML syntax matching nicely Catalog API > call > >> hive1.getFunction(ObjectPath functionName) where the database name is > >> absent for bulit-in functions available in that catalog hive1. I > understand > >> that Bowen's original proposal was trying to avoid this, but this could > >> turn out to be a clean
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all, Just an opinion on the built-in <> temporary functions resolution and NAMING issue. I think we should not allow overriding the built-in functions, as this may pose serious issues and to be honest is rather not feasible and would require major rework. What happens if a user wants to override CAST? Calls to that function are generated at different layers of the stack that unfortunately does not always go through the Catalog API (at least yet). Moreover from what I've checked no other systems allow overriding the built-in functions. All the systems I've checked so far register temporary functions in a database/schema (either special database for temporary functions, or just current database). What I would suggest is to always register temporary functions with a 3 part identifier. The same way as tables, views etc. This effectively means you cannot override built-in functions. With such approach it is natural that the temporary functions end up a step lower in the resolution order: 1. built-in functions (1 part, maybe 2? - this is still under discussion) 2. temporary functions (always 3 part path) 3. catalog functions (always 3 part path) Let me know what do you think. Best, Dawid On 04/09/2019 06:13, Bowen Li wrote: > Hi, > > I agree with Xuefu that the main controversial points are mainly the two > places. My thoughts on them: > > 1) Determinism of referencing Hive built-in functions. We can either remove > Hive built-in functions from ambiguous function resolution and require > users to use special syntax for their qualified names, or add a config flag > to catalog constructor/yaml for turning on and off Hive built-in functions > with the flag set to 'false' by default and proper doc added to help users > make their decisions. > > 2) Flink temp functions v.s. Flink built-in functions in ambiguous function > resolution order. We believe Flink temp functions should precede Flink > built-in functions, and I have presented my reasons. Just in case if we > cannot reach an agreement, I propose forbid users registering temp > functions in the same name as a built-in function, like MySQL's approach, > for the moment. It won't have any performance concern, since built-in > functions are all in memory and thus cost of a name check will be really > trivial. > > > On Tue, Sep 3, 2019 at 8:01 PM Xuefu Z wrote: > >> From what I have seen, there are a couple of focal disagreements: >> >> 1. Resolution order: temp function --> flink built-in function --> catalog >> function vs flink built-in function --> temp function -> catalog function. >> 2. "External" built-in functions: how to treat built-in functions in >> external system and how users reference them >> >> For #1, I agree with Bowen that temp function needs to be at the highest >> priority because that's how a user might overwrite a built-in function >> without referencing a persistent, overwriting catalog function with a fully >> qualified name. Putting built-in functions at the highest priority >> eliminates that usage. >> >> For #2, I saw a general agreement on referencing "external" built-in >> functions such as those in Hive needs to be explicit and deterministic even >> though different approaches are proposed. To limit the scope and simply the >> usage, it seems making sense to me to introduce special syntax for user to >> explicitly reference an external built-in function such as hive1::sqrt or >> hive1._built_in.sqrt. This is a DML syntax matching nicely Catalog API call >> hive1.getFunction(ObjectPath functionName) where the database name is >> absent for bulit-in functions available in that catalog hive1. I understand >> that Bowen's original proposal was trying to avoid this, but this could >> turn out to be a clean and simple solution. >> >> (Timo's modular approach is great way to "expand" Flink's built-in function >> set, which seems orthogonal and complementary to this, which could be >> tackled in further future work.) >> >> I'd be happy to hear further thoughts on the two points. >> >> Thanks, >> Xuefu >> >> On Tue, Sep 3, 2019 at 7:11 PM Kurt Young wrote: >> >>> Thanks Timo & Bowen for the feedback. Bowen was right, my proposal is the >>> same >>> as Bowen's. But after thinking about it, I'm currently lean to Timo's >>> suggestion. >>> >>> The reason is backward compatibility. If we follow Bowen's approach, >> let's >>> say we >>> first find function in Flink's built-in functions, and then hive's >>> built-in. For example, `foo` >>> is not supported by Flink, but hive has such built-in function. So user >>> will have hive's >>> behavior for function `foo`. And in next release, Flink realize this is a >>> very popular function >>> and add it into Flink's built-in functions, but with different behavior >> as >>> hive's. So in next >>> release, the behavior changes. >>> >>> With Timo's approach, IIUC user have to tell the framework explicitly >> what >>> kind of >>> built-in functions he would like to use. He can just tell
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi, I agree with Xuefu that the main controversial points are mainly the two places. My thoughts on them: 1) Determinism of referencing Hive built-in functions. We can either remove Hive built-in functions from ambiguous function resolution and require users to use special syntax for their qualified names, or add a config flag to catalog constructor/yaml for turning on and off Hive built-in functions with the flag set to 'false' by default and proper doc added to help users make their decisions. 2) Flink temp functions v.s. Flink built-in functions in ambiguous function resolution order. We believe Flink temp functions should precede Flink built-in functions, and I have presented my reasons. Just in case if we cannot reach an agreement, I propose forbid users registering temp functions in the same name as a built-in function, like MySQL's approach, for the moment. It won't have any performance concern, since built-in functions are all in memory and thus cost of a name check will be really trivial. On Tue, Sep 3, 2019 at 8:01 PM Xuefu Z wrote: > From what I have seen, there are a couple of focal disagreements: > > 1. Resolution order: temp function --> flink built-in function --> catalog > function vs flink built-in function --> temp function -> catalog function. > 2. "External" built-in functions: how to treat built-in functions in > external system and how users reference them > > For #1, I agree with Bowen that temp function needs to be at the highest > priority because that's how a user might overwrite a built-in function > without referencing a persistent, overwriting catalog function with a fully > qualified name. Putting built-in functions at the highest priority > eliminates that usage. > > For #2, I saw a general agreement on referencing "external" built-in > functions such as those in Hive needs to be explicit and deterministic even > though different approaches are proposed. To limit the scope and simply the > usage, it seems making sense to me to introduce special syntax for user to > explicitly reference an external built-in function such as hive1::sqrt or > hive1._built_in.sqrt. This is a DML syntax matching nicely Catalog API call > hive1.getFunction(ObjectPath functionName) where the database name is > absent for bulit-in functions available in that catalog hive1. I understand > that Bowen's original proposal was trying to avoid this, but this could > turn out to be a clean and simple solution. > > (Timo's modular approach is great way to "expand" Flink's built-in function > set, which seems orthogonal and complementary to this, which could be > tackled in further future work.) > > I'd be happy to hear further thoughts on the two points. > > Thanks, > Xuefu > > On Tue, Sep 3, 2019 at 7:11 PM Kurt Young wrote: > > > Thanks Timo & Bowen for the feedback. Bowen was right, my proposal is the > > same > > as Bowen's. But after thinking about it, I'm currently lean to Timo's > > suggestion. > > > > The reason is backward compatibility. If we follow Bowen's approach, > let's > > say we > > first find function in Flink's built-in functions, and then hive's > > built-in. For example, `foo` > > is not supported by Flink, but hive has such built-in function. So user > > will have hive's > > behavior for function `foo`. And in next release, Flink realize this is a > > very popular function > > and add it into Flink's built-in functions, but with different behavior > as > > hive's. So in next > > release, the behavior changes. > > > > With Timo's approach, IIUC user have to tell the framework explicitly > what > > kind of > > built-in functions he would like to use. He can just tell framework to > > abandon Flink's built-in > > functions, and use hive's instead. User can only choose between them, but > > not use > > them at the same time. I think this approach is more predictable. > > > > Best, > > Kurt > > > > > > On Wed, Sep 4, 2019 at 8:00 AM Bowen Li wrote: > > > > > Hi all, > > > > > > Thanks for the feedback. Just a kindly reminder that the [Proposal] > > section > > > in the google doc was updated, please take a look first and let me know > > if > > > you have more questions. > > > > > > On Tue, Sep 3, 2019 at 4:57 PM Bowen Li wrote: > > > > > > > Hi Timo, > > > > > > > > Re> 1) We should not have the restriction "hive built-in functions > can > > > > only > > > > > be used when current catalog is hive catalog". Switching a catalog > > > > > should only have implications on the cat.db.object resolution but > not > > > > > functions. It would be quite convinient for users to use Hive > > built-ins > > > > > even if they use a Confluent schema registry or just the in-memory > > > > catalog. > > > > > > > > There might be a misunderstanding here. > > > > > > > > First of all, Hive built-in functions are not part of Flink built-in > > > > functions, they are catalog functions, thus if the current catalog is > > > not a > > > > HiveCatalog but, say, a schema registry catalog, ambiguous
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thank you for your wonderful points. I like timo's proposal to enrich built-in functions to flexible function modules (For example, the financial model is useful to bank system). But I agree with bowen, I don't think hive functions deserves be a function module. I think all function modules should be flink built-in functions. In this way, we can control their standardization, rather than some controversial functions like hive. About Kurt's concern, yes, every addition of flink's function changes user behavior. But in the near future, we'll cover all of hive's functions (in the white list). So, if the final form does not have hive functions. sooner or later, this behavioral change will come. So do we need to let users choose? Back to the goal of hive built-in, I always thought it was just an intermediate solution. Do we need to provide hive built-in functions mode to users in the future? Best, Jingsong Lee -- From:Kurt Young Send Time:2019年9月4日(星期三) 10:11 To:dev Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog Thanks Timo & Bowen for the feedback. Bowen was right, my proposal is the same as Bowen's. But after thinking about it, I'm currently lean to Timo's suggestion. The reason is backward compatibility. If we follow Bowen's approach, let's say we first find function in Flink's built-in functions, and then hive's built-in. For example, `foo` is not supported by Flink, but hive has such built-in function. So user will have hive's behavior for function `foo`. And in next release, Flink realize this is a very popular function and add it into Flink's built-in functions, but with different behavior as hive's. So in next release, the behavior changes. With Timo's approach, IIUC user have to tell the framework explicitly what kind of built-in functions he would like to use. He can just tell framework to abandon Flink's built-in functions, and use hive's instead. User can only choose between them, but not use them at the same time. I think this approach is more predictable. Best, Kurt On Wed, Sep 4, 2019 at 8:00 AM Bowen Li wrote: > Hi all, > > Thanks for the feedback. Just a kindly reminder that the [Proposal] section > in the google doc was updated, please take a look first and let me know if > you have more questions. > > On Tue, Sep 3, 2019 at 4:57 PM Bowen Li wrote: > > > Hi Timo, > > > > Re> 1) We should not have the restriction "hive built-in functions can > > only > > > be used when current catalog is hive catalog". Switching a catalog > > > should only have implications on the cat.db.object resolution but not > > > functions. It would be quite convinient for users to use Hive built-ins > > > even if they use a Confluent schema registry or just the in-memory > > catalog. > > > > There might be a misunderstanding here. > > > > First of all, Hive built-in functions are not part of Flink built-in > > functions, they are catalog functions, thus if the current catalog is > not a > > HiveCatalog but, say, a schema registry catalog, ambiguous functions > > reference just shouldn't be resolved to a different catalog. > > > > Second, Hive built-in functions can potentially be referenced across > > catalog, but it doesn't have db namespace and we currently just don't > have > > a SQL syntax for it. It can be enabled when such a SQL syntax is defined, > > e.g. "catalog::function", but it's out of scope of this FLIP. > > > > 2) I would propose to have separate concepts for catalog and built-in > > functions. In particular it would be nice to modularize built-in > > functions. Some built-in functions are very crucial (like AS, CAST, > > MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe > > we add more experimental functions in the future or function for some > > special application area (Geo functions, ML functions). A data platform > > team might not want to make every built-in function available. Or a > > function module like ML functions is in a different Maven module. > > > > I think this is orthogonal to this FLIP, especially we don't have the > > "external built-in functions" anymore and currently the built-in function > > category remains untouched. > > > > But just to share some thoughts on the proposal, I'm not sure about it: > > - I don't know if any other databases handle built-in functions like > that. > > Maybe you can give some examples? IMHO, built-in functions are system > info > > and should be deterministic, not depending on loaded libraries. Geo > > functions should be either built-in already or just libraries functions, > > and library functions can be adapted to catalog APIs or of some other > > syntax to use > > - I don't know if all use cases stand, and many can be achieved by other > > approaches too. E.g. experimental functions can be taken good care of by > > documentations, annotations, etc > > - the proposal basically introduces some concept like a pluggable > built-in > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
>From what I have seen, there are a couple of focal disagreements: 1. Resolution order: temp function --> flink built-in function --> catalog function vs flink built-in function --> temp function -> catalog function. 2. "External" built-in functions: how to treat built-in functions in external system and how users reference them For #1, I agree with Bowen that temp function needs to be at the highest priority because that's how a user might overwrite a built-in function without referencing a persistent, overwriting catalog function with a fully qualified name. Putting built-in functions at the highest priority eliminates that usage. For #2, I saw a general agreement on referencing "external" built-in functions such as those in Hive needs to be explicit and deterministic even though different approaches are proposed. To limit the scope and simply the usage, it seems making sense to me to introduce special syntax for user to explicitly reference an external built-in function such as hive1::sqrt or hive1._built_in.sqrt. This is a DML syntax matching nicely Catalog API call hive1.getFunction(ObjectPath functionName) where the database name is absent for bulit-in functions available in that catalog hive1. I understand that Bowen's original proposal was trying to avoid this, but this could turn out to be a clean and simple solution. (Timo's modular approach is great way to "expand" Flink's built-in function set, which seems orthogonal and complementary to this, which could be tackled in further future work.) I'd be happy to hear further thoughts on the two points. Thanks, Xuefu On Tue, Sep 3, 2019 at 7:11 PM Kurt Young wrote: > Thanks Timo & Bowen for the feedback. Bowen was right, my proposal is the > same > as Bowen's. But after thinking about it, I'm currently lean to Timo's > suggestion. > > The reason is backward compatibility. If we follow Bowen's approach, let's > say we > first find function in Flink's built-in functions, and then hive's > built-in. For example, `foo` > is not supported by Flink, but hive has such built-in function. So user > will have hive's > behavior for function `foo`. And in next release, Flink realize this is a > very popular function > and add it into Flink's built-in functions, but with different behavior as > hive's. So in next > release, the behavior changes. > > With Timo's approach, IIUC user have to tell the framework explicitly what > kind of > built-in functions he would like to use. He can just tell framework to > abandon Flink's built-in > functions, and use hive's instead. User can only choose between them, but > not use > them at the same time. I think this approach is more predictable. > > Best, > Kurt > > > On Wed, Sep 4, 2019 at 8:00 AM Bowen Li wrote: > > > Hi all, > > > > Thanks for the feedback. Just a kindly reminder that the [Proposal] > section > > in the google doc was updated, please take a look first and let me know > if > > you have more questions. > > > > On Tue, Sep 3, 2019 at 4:57 PM Bowen Li wrote: > > > > > Hi Timo, > > > > > > Re> 1) We should not have the restriction "hive built-in functions can > > > only > > > > be used when current catalog is hive catalog". Switching a catalog > > > > should only have implications on the cat.db.object resolution but not > > > > functions. It would be quite convinient for users to use Hive > built-ins > > > > even if they use a Confluent schema registry or just the in-memory > > > catalog. > > > > > > There might be a misunderstanding here. > > > > > > First of all, Hive built-in functions are not part of Flink built-in > > > functions, they are catalog functions, thus if the current catalog is > > not a > > > HiveCatalog but, say, a schema registry catalog, ambiguous functions > > > reference just shouldn't be resolved to a different catalog. > > > > > > Second, Hive built-in functions can potentially be referenced across > > > catalog, but it doesn't have db namespace and we currently just don't > > have > > > a SQL syntax for it. It can be enabled when such a SQL syntax is > defined, > > > e.g. "catalog::function", but it's out of scope of this FLIP. > > > > > > 2) I would propose to have separate concepts for catalog and built-in > > > functions. In particular it would be nice to modularize built-in > > > functions. Some built-in functions are very crucial (like AS, CAST, > > > MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe > > > we add more experimental functions in the future or function for some > > > special application area (Geo functions, ML functions). A data platform > > > team might not want to make every built-in function available. Or a > > > function module like ML functions is in a different Maven module. > > > > > > I think this is orthogonal to this FLIP, especially we don't have the > > > "external built-in functions" anymore and currently the built-in > function > > > category remains untouched. > > > > > > But just to share some thoughts on the proposal,
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks Timo & Bowen for the feedback. Bowen was right, my proposal is the same as Bowen's. But after thinking about it, I'm currently lean to Timo's suggestion. The reason is backward compatibility. If we follow Bowen's approach, let's say we first find function in Flink's built-in functions, and then hive's built-in. For example, `foo` is not supported by Flink, but hive has such built-in function. So user will have hive's behavior for function `foo`. And in next release, Flink realize this is a very popular function and add it into Flink's built-in functions, but with different behavior as hive's. So in next release, the behavior changes. With Timo's approach, IIUC user have to tell the framework explicitly what kind of built-in functions he would like to use. He can just tell framework to abandon Flink's built-in functions, and use hive's instead. User can only choose between them, but not use them at the same time. I think this approach is more predictable. Best, Kurt On Wed, Sep 4, 2019 at 8:00 AM Bowen Li wrote: > Hi all, > > Thanks for the feedback. Just a kindly reminder that the [Proposal] section > in the google doc was updated, please take a look first and let me know if > you have more questions. > > On Tue, Sep 3, 2019 at 4:57 PM Bowen Li wrote: > > > Hi Timo, > > > > Re> 1) We should not have the restriction "hive built-in functions can > > only > > > be used when current catalog is hive catalog". Switching a catalog > > > should only have implications on the cat.db.object resolution but not > > > functions. It would be quite convinient for users to use Hive built-ins > > > even if they use a Confluent schema registry or just the in-memory > > catalog. > > > > There might be a misunderstanding here. > > > > First of all, Hive built-in functions are not part of Flink built-in > > functions, they are catalog functions, thus if the current catalog is > not a > > HiveCatalog but, say, a schema registry catalog, ambiguous functions > > reference just shouldn't be resolved to a different catalog. > > > > Second, Hive built-in functions can potentially be referenced across > > catalog, but it doesn't have db namespace and we currently just don't > have > > a SQL syntax for it. It can be enabled when such a SQL syntax is defined, > > e.g. "catalog::function", but it's out of scope of this FLIP. > > > > 2) I would propose to have separate concepts for catalog and built-in > > functions. In particular it would be nice to modularize built-in > > functions. Some built-in functions are very crucial (like AS, CAST, > > MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe > > we add more experimental functions in the future or function for some > > special application area (Geo functions, ML functions). A data platform > > team might not want to make every built-in function available. Or a > > function module like ML functions is in a different Maven module. > > > > I think this is orthogonal to this FLIP, especially we don't have the > > "external built-in functions" anymore and currently the built-in function > > category remains untouched. > > > > But just to share some thoughts on the proposal, I'm not sure about it: > > - I don't know if any other databases handle built-in functions like > that. > > Maybe you can give some examples? IMHO, built-in functions are system > info > > and should be deterministic, not depending on loaded libraries. Geo > > functions should be either built-in already or just libraries functions, > > and library functions can be adapted to catalog APIs or of some other > > syntax to use > > - I don't know if all use cases stand, and many can be achieved by other > > approaches too. E.g. experimental functions can be taken good care of by > > documentations, annotations, etc > > - the proposal basically introduces some concept like a pluggable > built-in > > function catalog, despite the already existing catalog APIs > > - it brings in even more complicated scenarios to the design. E.g. how do > > you handle built-in functions in different modules but different names? > > > > In short, I'm not sure if it really stands and it looks like an overkill > > to me. I'd rather not go to that route. Related discussion can be on its > > own thread. > > > > 3) Following the suggestion above, we can have a separate discovery > > mechanism for built-in functions. Instead of just going through a static > > list like in BuiltInFunctionDefinitions, a platform team should be able > > to select function modules like > > catalogManager.setFunctionModules(CoreFunctions, GeoFunctions, > > HiveFunctions) or via service discovery; > > > > Same as above. I'll leave it to its own thread. > > > > re > 3) Dawid and I discussed the resulution order again. I agree with > > Kurt > > > that we should unify built-in function (external or internal) under a > > > common layer. However, the resolution order should be: > > > 1. built-in functions > > > 2. temporary functions > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi all, Thanks for the feedback. Just a kindly reminder that the [Proposal] section in the google doc was updated, please take a look first and let me know if you have more questions. On Tue, Sep 3, 2019 at 4:57 PM Bowen Li wrote: > Hi Timo, > > Re> 1) We should not have the restriction "hive built-in functions can > only > > be used when current catalog is hive catalog". Switching a catalog > > should only have implications on the cat.db.object resolution but not > > functions. It would be quite convinient for users to use Hive built-ins > > even if they use a Confluent schema registry or just the in-memory > catalog. > > There might be a misunderstanding here. > > First of all, Hive built-in functions are not part of Flink built-in > functions, they are catalog functions, thus if the current catalog is not a > HiveCatalog but, say, a schema registry catalog, ambiguous functions > reference just shouldn't be resolved to a different catalog. > > Second, Hive built-in functions can potentially be referenced across > catalog, but it doesn't have db namespace and we currently just don't have > a SQL syntax for it. It can be enabled when such a SQL syntax is defined, > e.g. "catalog::function", but it's out of scope of this FLIP. > > 2) I would propose to have separate concepts for catalog and built-in > functions. In particular it would be nice to modularize built-in > functions. Some built-in functions are very crucial (like AS, CAST, > MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe > we add more experimental functions in the future or function for some > special application area (Geo functions, ML functions). A data platform > team might not want to make every built-in function available. Or a > function module like ML functions is in a different Maven module. > > I think this is orthogonal to this FLIP, especially we don't have the > "external built-in functions" anymore and currently the built-in function > category remains untouched. > > But just to share some thoughts on the proposal, I'm not sure about it: > - I don't know if any other databases handle built-in functions like that. > Maybe you can give some examples? IMHO, built-in functions are system info > and should be deterministic, not depending on loaded libraries. Geo > functions should be either built-in already or just libraries functions, > and library functions can be adapted to catalog APIs or of some other > syntax to use > - I don't know if all use cases stand, and many can be achieved by other > approaches too. E.g. experimental functions can be taken good care of by > documentations, annotations, etc > - the proposal basically introduces some concept like a pluggable built-in > function catalog, despite the already existing catalog APIs > - it brings in even more complicated scenarios to the design. E.g. how do > you handle built-in functions in different modules but different names? > > In short, I'm not sure if it really stands and it looks like an overkill > to me. I'd rather not go to that route. Related discussion can be on its > own thread. > > 3) Following the suggestion above, we can have a separate discovery > mechanism for built-in functions. Instead of just going through a static > list like in BuiltInFunctionDefinitions, a platform team should be able > to select function modules like > catalogManager.setFunctionModules(CoreFunctions, GeoFunctions, > HiveFunctions) or via service discovery; > > Same as above. I'll leave it to its own thread. > > re > 3) Dawid and I discussed the resulution order again. I agree with > Kurt > > that we should unify built-in function (external or internal) under a > > common layer. However, the resolution order should be: > > 1. built-in functions > > 2. temporary functions > > 3. regular catalog resolution logic > > Otherwise a temporary function could cause clashes with Flink's built-in > > functions. If you take a look at other vendors, like SQL Server they > > also do not allow to overwrite built-in functions. > > ”I agree with Kurt that we should unify built-in function (external or > internal) under a common layer.“ <- I don't think this is what Kurt means. > Kurt and I are in favor of unifying built-in functions of external systems > and catalog functions. Did you type a mistake? > > Besides, I'm not sure about the resolution order you proposed. Temporary > functions have a lifespan over a session and are only visible to the > session owner, they are unique to each user, and users create them on > purpose to be the highest priority in order to overwrite system info > (built-in functions in this case). > > In your case, why would users name a temporary function the same as a > built-in function then? Since using that name in ambiguous function > reference will always be resolved to built-in functions, creating a > same-named temp function would be meaningless in the end. > > > On Tue, Sep 3, 2019 at 1:44 PM Bowen Li wrote: > >> Hi Jingsong, >> >> Re>
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Timo, Re> 1) We should not have the restriction "hive built-in functions can only > be used when current catalog is hive catalog". Switching a catalog > should only have implications on the cat.db.object resolution but not > functions. It would be quite convinient for users to use Hive built-ins > even if they use a Confluent schema registry or just the in-memory catalog. There might be a misunderstanding here. First of all, Hive built-in functions are not part of Flink built-in functions, they are catalog functions, thus if the current catalog is not a HiveCatalog but, say, a schema registry catalog, ambiguous functions reference just shouldn't be resolved to a different catalog. Second, Hive built-in functions can potentially be referenced across catalog, but it doesn't have db namespace and we currently just don't have a SQL syntax for it. It can be enabled when such a SQL syntax is defined, e.g. "catalog::function", but it's out of scope of this FLIP. 2) I would propose to have separate concepts for catalog and built-in functions. In particular it would be nice to modularize built-in functions. Some built-in functions are very crucial (like AS, CAST, MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe we add more experimental functions in the future or function for some special application area (Geo functions, ML functions). A data platform team might not want to make every built-in function available. Or a function module like ML functions is in a different Maven module. I think this is orthogonal to this FLIP, especially we don't have the "external built-in functions" anymore and currently the built-in function category remains untouched. But just to share some thoughts on the proposal, I'm not sure about it: - I don't know if any other databases handle built-in functions like that. Maybe you can give some examples? IMHO, built-in functions are system info and should be deterministic, not depending on loaded libraries. Geo functions should be either built-in already or just libraries functions, and library functions can be adapted to catalog APIs or of some other syntax to use - I don't know if all use cases stand, and many can be achieved by other approaches too. E.g. experimental functions can be taken good care of by documentations, annotations, etc - the proposal basically introduces some concept like a pluggable built-in function catalog, despite the already existing catalog APIs - it brings in even more complicated scenarios to the design. E.g. how do you handle built-in functions in different modules but different names? In short, I'm not sure if it really stands and it looks like an overkill to me. I'd rather not go to that route. Related discussion can be on its own thread. 3) Following the suggestion above, we can have a separate discovery mechanism for built-in functions. Instead of just going through a static list like in BuiltInFunctionDefinitions, a platform team should be able to select function modules like catalogManager.setFunctionModules(CoreFunctions, GeoFunctions, HiveFunctions) or via service discovery; Same as above. I'll leave it to its own thread. re > 3) Dawid and I discussed the resulution order again. I agree with Kurt > that we should unify built-in function (external or internal) under a > common layer. However, the resolution order should be: > 1. built-in functions > 2. temporary functions > 3. regular catalog resolution logic > Otherwise a temporary function could cause clashes with Flink's built-in > functions. If you take a look at other vendors, like SQL Server they > also do not allow to overwrite built-in functions. ”I agree with Kurt that we should unify built-in function (external or internal) under a common layer.“ <- I don't think this is what Kurt means. Kurt and I are in favor of unifying built-in functions of external systems and catalog functions. Did you type a mistake? Besides, I'm not sure about the resolution order you proposed. Temporary functions have a lifespan over a session and are only visible to the session owner, they are unique to each user, and users create them on purpose to be the highest priority in order to overwrite system info (built-in functions in this case). In your case, why would users name a temporary function the same as a built-in function then? Since using that name in ambiguous function reference will always be resolved to built-in functions, creating a same-named temp function would be meaningless in the end. On Tue, Sep 3, 2019 at 1:44 PM Bowen Li wrote: > Hi Jingsong, > > Re> 1.Hive built-in functions is an intermediate solution. So we should > > not introduce interfaces to influence the framework. To make > > Flink itself more powerful, we should implement the functions > > we need to add. > > Yes, please see the doc. > > Re> 2.Non-flink built-in functions are easy for users to change their > > behavior. If we support some flink built-in functions in the > > future but act
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Jingsong, Re> 1.Hive built-in functions is an intermediate solution. So we should > not introduce interfaces to influence the framework. To make > Flink itself more powerful, we should implement the functions > we need to add. Yes, please see the doc. Re> 2.Non-flink built-in functions are easy for users to change their > behavior. If we support some flink built-in functions in the > future but act differently from non-flink built-in, this will lead to > changes in user behavior. There's no such concept as "external built-in functions" any more. Built-in functions of external systems will be treated as special catalog functions. Re> Another question is, does this fallback include all > hive built-in functions? As far as I know, some hive functions > have some hacky. If possible, can we start with a white list? > Once we implement some functions to flink built-in, we can > also update the whitelist. Yes, that's something we thought of too. I don't think it's super critical to the scope of this FLIP, thus I'd like to leave it to future efforts as a nice-to-have feature. On Tue, Sep 3, 2019 at 1:37 PM Bowen Li wrote: > Hi Kurt, > > Re: > What I want to propose is we can merge #3 and #4, make them both > under > >"catalog" concept, by extending catalog function to make it have ability > to > >have built-in catalog functions. Some benefits I can see from this > approach: > >1. We don't have to introduce new concept like external built-in > functions. > >Actually I don't see a full story about how to treat a built-in > functions, and it > >seems a little bit disrupt with catalog. As a result, you have to make > some restriction > >like "hive built-in functions can only be used when current catalog is > hive catalog". > > Yes, I've unified #3 and #4 but it seems I didn't update some part of the > doc. I've modified those sections, and they are up to date now. > > In short, now built-in function of external systems are defined as a > special kind of catalog function in Flink, and handled by Flink as > following: > - An external built-in function must be associated with a catalog for the > purpose of decoupling flink-table and external systems. > - It always resides in front of catalog functions in ambiguous function > reference order, just like in its own external system > - It is a special catalog function that doesn’t have a schema/database > namespace > - It goes thru the same instantiation logic as other user defined catalog > functions in the external system > > Please take another look at the doc, and let me know if you have more > questions. > > > On Tue, Sep 3, 2019 at 7:28 AM Timo Walther wrote: > >> Hi Kurt, >> >> it should not affect the functions and operations we currently have in >> SQL. It just categorizes the available built-in functions. It is kind of >> an orthogonal concept to the catalog API but built-in functions deserve >> this special kind of treatment. CatalogFunction still fits perfectly in >> there because the regular catalog object resolution logic is not >> affected. So tables and functions are resolved in the same way but with >> built-in functions that have priority as in the original design. >> >> Regards, >> Timo >> >> >> On 03.09.19 15:26, Kurt Young wrote: >> > Does this only affect the functions and operations we currently have in >> SQL >> > and >> > have no effect on tables, right? Looks like this is an orthogonal >> concept >> > with Catalog? >> > If the answer are both yes, then the catalog function will be a weird >> > concept? >> > >> > Best, >> > Kurt >> > >> > >> > On Tue, Sep 3, 2019 at 8:10 PM Danny Chan wrote: >> > >> >> The way you proposed are basically the same as what Calcite does, I >> think >> >> we are in the same line. >> >> >> >> Best, >> >> Danny Chan >> >> 在 2019年9月3日 +0800 PM7:57，Timo Walther ，写道： >> >>> This sounds exactly as the module approach I mentioned, no? >> >>> >> >>> Regards, >> >>> Timo >> >>> >> >>> On 03.09.19 13:42, Danny Chan wrote: >> Thanks Bowen for bring up this topic, I think it’s a useful >> >> refactoring to make our function usage more user friendly. >> For the topic of how to organize the builtin operators and operators >> >> of Hive, here is a solution from Apache Calcite, the Calcite way is to >> make >> >> every dialect operators a “Library”, user can specify which libraries >> they >> >> want to use for a sql query. The builtin operators always comes as the >> >> first class objects and the others are used from the order they >> appears. >> >> Maybe you can take a reference. >> [1] >> >> >> https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 >> Best, >> Danny Chan >> 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： >> > Hi folks, >> > >> > I'd like to kick off a discussion on reworking Flink's >> >> FunctionCatalog. >> > It's critically helpful to improve function usability in SQL. >> > >> > >> >> >>
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Kurt, Re: > What I want to propose is we can merge #3 and #4, make them both under >"catalog" concept, by extending catalog function to make it have ability to >have built-in catalog functions. Some benefits I can see from this approach: >1. We don't have to introduce new concept like external built-in functions. >Actually I don't see a full story about how to treat a built-in functions, and it >seems a little bit disrupt with catalog. As a result, you have to make some restriction >like "hive built-in functions can only be used when current catalog is hive catalog". Yes, I've unified #3 and #4 but it seems I didn't update some part of the doc. I've modified those sections, and they are up to date now. In short, now built-in function of external systems are defined as a special kind of catalog function in Flink, and handled by Flink as following: - An external built-in function must be associated with a catalog for the purpose of decoupling flink-table and external systems. - It always resides in front of catalog functions in ambiguous function reference order, just like in its own external system - It is a special catalog function that doesn’t have a schema/database namespace - It goes thru the same instantiation logic as other user defined catalog functions in the external system Please take another look at the doc, and let me know if you have more questions. On Tue, Sep 3, 2019 at 7:28 AM Timo Walther wrote: > Hi Kurt, > > it should not affect the functions and operations we currently have in > SQL. It just categorizes the available built-in functions. It is kind of > an orthogonal concept to the catalog API but built-in functions deserve > this special kind of treatment. CatalogFunction still fits perfectly in > there because the regular catalog object resolution logic is not > affected. So tables and functions are resolved in the same way but with > built-in functions that have priority as in the original design. > > Regards, > Timo > > > On 03.09.19 15:26, Kurt Young wrote: > > Does this only affect the functions and operations we currently have in > SQL > > and > > have no effect on tables, right? Looks like this is an orthogonal concept > > with Catalog? > > If the answer are both yes, then the catalog function will be a weird > > concept? > > > > Best, > > Kurt > > > > > > On Tue, Sep 3, 2019 at 8:10 PM Danny Chan wrote: > > > >> The way you proposed are basically the same as what Calcite does, I > think > >> we are in the same line. > >> > >> Best, > >> Danny Chan > >> 在 2019年9月3日 +0800 PM7:57，Timo Walther ，写道： > >>> This sounds exactly as the module approach I mentioned, no? > >>> > >>> Regards, > >>> Timo > >>> > >>> On 03.09.19 13:42, Danny Chan wrote: > Thanks Bowen for bring up this topic, I think it’s a useful > >> refactoring to make our function usage more user friendly. > For the topic of how to organize the builtin operators and operators > >> of Hive, here is a solution from Apache Calcite, the Calcite way is to > make > >> every dialect operators a “Library”, user can specify which libraries > they > >> want to use for a sql query. The builtin operators always comes as the > >> first class objects and the others are used from the order they appears. > >> Maybe you can take a reference. > [1] > >> > https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 > Best, > Danny Chan > 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： > > Hi folks, > > > > I'd like to kick off a discussion on reworking Flink's > >> FunctionCatalog. > > It's critically helpful to improve function usability in SQL. > > > > > >> > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > In short, it: > > - adds support for precise function reference with fully/partially > > qualified name > > - redefines function resolution order for ambiguous function > >> reference > > - adds support for Hive's rich built-in functions (support for Hive > >> user > > defined functions was already added in 1.9.0) > > - clarifies the concept of temporary functions > > > > Would love to hear your thoughts. > > > > Bowen > >>> > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Kurt, it should not affect the functions and operations we currently have in SQL. It just categorizes the available built-in functions. It is kind of an orthogonal concept to the catalog API but built-in functions deserve this special kind of treatment. CatalogFunction still fits perfectly in there because the regular catalog object resolution logic is not affected. So tables and functions are resolved in the same way but with built-in functions that have priority as in the original design. Regards, Timo On 03.09.19 15:26, Kurt Young wrote: Does this only affect the functions and operations we currently have in SQL and have no effect on tables, right? Looks like this is an orthogonal concept with Catalog? If the answer are both yes, then the catalog function will be a weird concept? Best, Kurt On Tue, Sep 3, 2019 at 8:10 PM Danny Chan wrote: The way you proposed are basically the same as what Calcite does, I think we are in the same line. Best, Danny Chan 在 2019年9月3日 +0800 PM7:57，Timo Walther ，写道： This sounds exactly as the module approach I mentioned, no? Regards, Timo On 03.09.19 13:42, Danny Chan wrote: Thanks Bowen for bring up this topic, I think it’s a useful refactoring to make our function usage more user friendly. For the topic of how to organize the builtin operators and operators of Hive, here is a solution from Apache Calcite, the Calcite way is to make every dialect operators a “Library”, user can specify which libraries they want to use for a sql query. The builtin operators always comes as the first class objects and the others are used from the order they appears. Maybe you can take a reference. [1] https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 Best, Danny Chan 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： Hi folks, I'd like to kick off a discussion on reworking Flink's FunctionCatalog. It's critically helpful to improve function usability in SQL. https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing In short, it: - adds support for precise function reference with fully/partially qualified name - redefines function resolution order for ambiguous function reference - adds support for Hive's rich built-in functions (support for Hive user defined functions was already added in 1.9.0) - clarifies the concept of temporary functions Would love to hear your thoughts. Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Does this only affect the functions and operations we currently have in SQL and have no effect on tables, right? Looks like this is an orthogonal concept with Catalog? If the answer are both yes, then the catalog function will be a weird concept? Best, Kurt On Tue, Sep 3, 2019 at 8:10 PM Danny Chan wrote: > The way you proposed are basically the same as what Calcite does, I think > we are in the same line. > > Best, > Danny Chan > 在 2019年9月3日 +0800 PM7:57，Timo Walther ，写道： > > This sounds exactly as the module approach I mentioned, no? > > > > Regards, > > Timo > > > > On 03.09.19 13:42, Danny Chan wrote: > > > Thanks Bowen for bring up this topic, I think it’s a useful > refactoring to make our function usage more user friendly. > > > > > > For the topic of how to organize the builtin operators and operators > of Hive, here is a solution from Apache Calcite, the Calcite way is to make > every dialect operators a “Library”, user can specify which libraries they > want to use for a sql query. The builtin operators always comes as the > first class objects and the others are used from the order they appears. > Maybe you can take a reference. > > > > > > [1] > https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 > > > > > > Best, > > > Danny Chan > > > 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： > > > > Hi folks, > > > > > > > > I'd like to kick off a discussion on reworking Flink's > FunctionCatalog. > > > > It's critically helpful to improve function usability in SQL. > > > > > > > > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > > > > > > > In short, it: > > > > - adds support for precise function reference with fully/partially > > > > qualified name > > > > - redefines function resolution order for ambiguous function > reference > > > > - adds support for Hive's rich built-in functions (support for Hive > user > > > > defined functions was already added in 1.9.0) > > > > - clarifies the concept of temporary functions > > > > > > > > Would love to hear your thoughts. > > > > > > > > Bowen > > > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
The way you proposed are basically the same as what Calcite does, I think we are in the same line. Best, Danny Chan 在 2019年9月3日 +0800 PM7:57，Timo Walther ，写道： > This sounds exactly as the module approach I mentioned, no? > > Regards, > Timo > > On 03.09.19 13:42, Danny Chan wrote: > > Thanks Bowen for bring up this topic, I think it’s a useful refactoring to > > make our function usage more user friendly. > > > > For the topic of how to organize the builtin operators and operators of > > Hive, here is a solution from Apache Calcite, the Calcite way is to make > > every dialect operators a “Library”, user can specify which libraries they > > want to use for a sql query. The builtin operators always comes as the > > first class objects and the others are used from the order they appears. > > Maybe you can take a reference. > > > > [1] > > https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 > > > > Best, > > Danny Chan > > 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： > > > Hi folks, > > > > > > I'd like to kick off a discussion on reworking Flink's FunctionCatalog. > > > It's critically helpful to improve function usability in SQL. > > > > > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > > > > > In short, it: > > > - adds support for precise function reference with fully/partially > > > qualified name > > > - redefines function resolution order for ambiguous function reference > > > - adds support for Hive's rich built-in functions (support for Hive user > > > defined functions was already added in 1.9.0) > > > - clarifies the concept of temporary functions > > > > > > Would love to hear your thoughts. > > > > > > Bowen > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
This sounds exactly as the module approach I mentioned, no? Regards, Timo On 03.09.19 13:42, Danny Chan wrote: Thanks Bowen for bring up this topic, I think it’s a useful refactoring to make our function usage more user friendly. For the topic of how to organize the builtin operators and operators of Hive, here is a solution from Apache Calcite, the Calcite way is to make every dialect operators a “Library”, user can specify which libraries they want to use for a sql query. The builtin operators always comes as the first class objects and the others are used from the order they appears. Maybe you can take a reference. [1] https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 Best, Danny Chan 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： Hi folks, I'd like to kick off a discussion on reworking Flink's FunctionCatalog. It's critically helpful to improve function usability in SQL. https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing In short, it: - adds support for precise function reference with fully/partially qualified name - redefines function resolution order for ambiguous function reference - adds support for Hive's rich built-in functions (support for Hive user defined functions was already added in 1.9.0) - clarifies the concept of temporary functions Would love to hear your thoughts. Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks Bowen for bring up this topic, I think it’s a useful refactoring to make our function usage more user friendly. For the topic of how to organize the builtin operators and operators of Hive, here is a solution from Apache Calcite, the Calcite way is to make every dialect operators a “Library”, user can specify which libraries they want to use for a sql query. The builtin operators always comes as the first class objects and the others are used from the order they appears. Maybe you can take a reference. [1] https://github.com/apache/calcite/commit/9a4eab5240d96379431d14a1ac33bfebaf6fbb28 Best, Danny Chan 在 2019年8月28日 +0800 AM2:50，Bowen Li ，写道： > Hi folks, > > I'd like to kick off a discussion on reworking Flink's FunctionCatalog. > It's critically helpful to improve function usability in SQL. > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > In short, it: > - adds support for precise function reference with fully/partially > qualified name > - redefines function resolution order for ambiguous function reference > - adds support for Hive's rich built-in functions (support for Hive user > defined functions was already added in 1.9.0) > - clarifies the concept of temporary functions > > Would love to hear your thoughts. > > Bowen
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Hi Bowen, thanks for your proposal. Here are some thoughts: 1) We should not have the restriction "hive built-in functions can only be used when current catalog is hive catalog". Switching a catalog should only have implications on the cat.db.object resolution but not functions. It would be quite convinient for users to use Hive built-ins even if they use a Confluent schema registry or just the in-memory catalog. 2) I would propose to have separate concepts for catalog and built-in functions. In particular it would be nice to modularize built-in functions. Some built-in functions are very crucial (like AS, CAST, MINUS), others are more optional but stable (MD5, CONCAT_WS), and maybe we add more experimental functions in the future or function for some special application area (Geo functions, ML functions). A data platform team might not want to make every built-in function available. Or a function module like ML functions is in a different Maven module. 3) Following the suggestion above, we can have a separate discovery mechanism for built-in functions. Instead of just going through a static list like in BuiltInFunctionDefinitions, a platform team should be able to select function modules like catalogManager.setFunctionModules(CoreFunctions, GeoFunctions, HiveFunctions) or via service discovery; 3) Dawid and I discussed the resulution order again. I agree with Kurt that we should unify built-in function (external or internal) under a common layer. However, the resolution order should be: 1. built-in functions 2. temporary functions 3. regular catalog resolution logic Otherwise a temporary function could cause clashes with Flink's built-in functions. If you take a look at other vendors, like SQL Server they also do not allow to overwrite built-in functions. Regards, Timo On 03.09.19 10:35, JingsongLee wrote: Thanks Bowen: +1 for this. And +1 to Kurt's suggestion. My other points are: 1.Hive built-in functions is an intermediate solution. So we should not introduce interfaces to influence the framework. To make Flink itself more powerful, we should implement the functions we need to add. 2.Non-flink built-in functions are easy for users to change their behavior. If we support some flink built-in functions in the future but act differently from non-flink built-in, this will lead to changes in user behavior. 3.Fallback to Non-flink built-in functions is a bad choice to performance. Without flink internal codegen and data format, and bring data format conversion, the performance is not so good. We need to support more complete hive jobs now, we need to have this fallback strategy. But it's not worth adding this concept at the catalog interface level, and it's not worth encouraging other catalogs to do so. Another question is, does this fallback include all hive built-in functions? As far as I know, some hive functions have some hacky. If possible, can we start with a white list? Once we implement some functions to flink built-in, we can also update the whitelist. Best, Jingsong Lee -- From:Kurt Young Send Time:2019年9月3日(星期二) 15:41 To:dev Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog Thanks Bowen for driving this. +1 for the general idea. It makes the function resolved behavior more clear and deterministic. Besides, the user can use all hive built-in functions, which is a great feature. I only have one comment, but maybe it may touch your design so I think it would make sense to reply this mail instead of comment on google doc. Regarding to the classfication of functions, you currently have 4 types of functions, which are: 1. temporary functions 2. Flink built-in functions 3. Hive built-in functions (or generalized as external built-in functions) 4. catalog functions What I want to propose is we can merge #3 and #4, make them both under "catalog" concept, by extending catalog function to make it have ability to have built-in catalog functions. Some benefits I can see from this approach: 1. We don't have to introduce new concept like external built-in functions. Actually I don't see a full story about how to treat a built-in functions, and it seems a little bit disrupt with catalog. As a result, you have to make some restriction like "hive built-in functions can only be used when current catalog is hive catalog". 2. It makes us easier to adopt another system's built-in functions to Flink, such as MySQL. If we don't treat uniformly with "external built-in functions" and "external catalog function", things like user set current catalog to hive but want to use MySQL's built-in function will happen. One more thing, follow this approach, it's clear for your question about how to support external built-in functions, which is "add a getBuiltInFunction to current Catalog API". What do you think? Best, Kurt On Fri, Aug 30, 2019 at 7:14 AM Bowen Li wrote:
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks Bowen: +1 for this. And +1 to Kurt's suggestion. My other points are: 1.Hive built-in functions is an intermediate solution. So we should not introduce interfaces to influence the framework. To make Flink itself more powerful, we should implement the functions we need to add. 2.Non-flink built-in functions are easy for users to change their behavior. If we support some flink built-in functions in the future but act differently from non-flink built-in, this will lead to changes in user behavior. 3.Fallback to Non-flink built-in functions is a bad choice to performance. Without flink internal codegen and data format, and bring data format conversion, the performance is not so good. We need to support more complete hive jobs now, we need to have this fallback strategy. But it's not worth adding this concept at the catalog interface level, and it's not worth encouraging other catalogs to do so. Another question is, does this fallback include all hive built-in functions? As far as I know, some hive functions have some hacky. If possible, can we start with a white list? Once we implement some functions to flink built-in, we can also update the whitelist. Best, Jingsong Lee -- From:Kurt Young Send Time:2019年9月3日(星期二) 15:41 To:dev Subject:Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog Thanks Bowen for driving this. +1 for the general idea. It makes the function resolved behavior more clear and deterministic. Besides, the user can use all hive built-in functions, which is a great feature. I only have one comment, but maybe it may touch your design so I think it would make sense to reply this mail instead of comment on google doc. Regarding to the classfication of functions, you currently have 4 types of functions, which are: 1. temporary functions 2. Flink built-in functions 3. Hive built-in functions (or generalized as external built-in functions) 4. catalog functions What I want to propose is we can merge #3 and #4, make them both under "catalog" concept, by extending catalog function to make it have ability to have built-in catalog functions. Some benefits I can see from this approach: 1. We don't have to introduce new concept like external built-in functions. Actually I don't see a full story about how to treat a built-in functions, and it seems a little bit disrupt with catalog. As a result, you have to make some restriction like "hive built-in functions can only be used when current catalog is hive catalog". 2. It makes us easier to adopt another system's built-in functions to Flink, such as MySQL. If we don't treat uniformly with "external built-in functions" and "external catalog function", things like user set current catalog to hive but want to use MySQL's built-in function will happen. One more thing, follow this approach, it's clear for your question about how to support external built-in functions, which is "add a getBuiltInFunction to current Catalog API". What do you think? Best, Kurt On Fri, Aug 30, 2019 at 7:14 AM Bowen Li wrote: > Thanks everyone for the feedback. > > I have updated the document accordingly. Here're the summary of changes: > > - clarify the concept of temporary functions, to facilitate deciding > function resolution order > - provide two options to support Hive built-in functions, with the 2nd one > being preferred > - add detailed prototype code for FunctionCatalog#lookupFunction(name) > - move the section of ”rename existing FunctionCatalog APIs in favor of > temporary functions“ out of the scope of the FLIP > - add another reasonable limitation for function resolution, to not > consider resolving overloaded functions - those with the same name but > different params. (It's still valid to have a single function with > overloaded eval() methods) > > Please take another look. > > Thanks, > Bowen > > On Tue, Aug 27, 2019 at 11:49 AM Bowen Li wrote: > > > Hi folks, > > > > I'd like to kick off a discussion on reworking Flink's FunctionCatalog. > > It's critically helpful to improve function usability in SQL. > > > > > > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > > > In short, it: > > - adds support for precise function reference with fully/partially > > qualified name > > - redefines function resolution order for ambiguous function reference > > - adds support for Hive's rich built-in functions (support for Hive user > > defined functions was already added in 1.9.0) > > - clarifies the concept of temporary functions > > > > Would love to hear your thoughts. > > > > Bowen > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks Bowen for driving this. +1 for the general idea. It makes the function resolved behavior more clear and deterministic. Besides, the user can use all hive built-in functions, which is a great feature. I only have one comment, but maybe it may touch your design so I think it would make sense to reply this mail instead of comment on google doc. Regarding to the classfication of functions, you currently have 4 types of functions, which are: 1. temporary functions 2. Flink built-in functions 3. Hive built-in functions (or generalized as external built-in functions) 4. catalog functions What I want to propose is we can merge #3 and #4, make them both under "catalog" concept, by extending catalog function to make it have ability to have built-in catalog functions. Some benefits I can see from this approach: 1. We don't have to introduce new concept like external built-in functions. Actually I don't see a full story about how to treat a built-in functions, and it seems a little bit disrupt with catalog. As a result, you have to make some restriction like "hive built-in functions can only be used when current catalog is hive catalog". 2. It makes us easier to adopt another system's built-in functions to Flink, such as MySQL. If we don't treat uniformly with "external built-in functions" and "external catalog function", things like user set current catalog to hive but want to use MySQL's built-in function will happen. One more thing, follow this approach, it's clear for your question about how to support external built-in functions, which is "add a getBuiltInFunction to current Catalog API". What do you think? Best, Kurt On Fri, Aug 30, 2019 at 7:14 AM Bowen Li wrote: > Thanks everyone for the feedback. > > I have updated the document accordingly. Here're the summary of changes: > > - clarify the concept of temporary functions, to facilitate deciding > function resolution order > - provide two options to support Hive built-in functions, with the 2nd one > being preferred > - add detailed prototype code for FunctionCatalog#lookupFunction(name) > - move the section of ”rename existing FunctionCatalog APIs in favor of > temporary functions“ out of the scope of the FLIP > - add another reasonable limitation for function resolution, to not > consider resolving overloaded functions - those with the same name but > different params. (It's still valid to have a single function with > overloaded eval() methods) > > Please take another look. > > Thanks, > Bowen > > On Tue, Aug 27, 2019 at 11:49 AM Bowen Li wrote: > > > Hi folks, > > > > I'd like to kick off a discussion on reworking Flink's FunctionCatalog. > > It's critically helpful to improve function usability in SQL. > > > > > > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > > > In short, it: > > - adds support for precise function reference with fully/partially > > qualified name > > - redefines function resolution order for ambiguous function reference > > - adds support for Hive's rich built-in functions (support for Hive user > > defined functions was already added in 1.9.0) > > - clarifies the concept of temporary functions > > > > Would love to hear your thoughts. > > > > Bowen > > >
Re: [DISCUSS] FLIP-57 - Rework FunctionCatalog
Thanks everyone for the feedback. I have updated the document accordingly. Here're the summary of changes: - clarify the concept of temporary functions, to facilitate deciding function resolution order - provide two options to support Hive built-in functions, with the 2nd one being preferred - add detailed prototype code for FunctionCatalog#lookupFunction(name) - move the section of ”rename existing FunctionCatalog APIs in favor of temporary functions“ out of the scope of the FLIP - add another reasonable limitation for function resolution, to not consider resolving overloaded functions - those with the same name but different params. (It's still valid to have a single function with overloaded eval() methods) Please take another look. Thanks, Bowen On Tue, Aug 27, 2019 at 11:49 AM Bowen Li wrote: > Hi folks, > > I'd like to kick off a discussion on reworking Flink's FunctionCatalog. > It's critically helpful to improve function usability in SQL. > > > https://docs.google.com/document/d/1w3HZGj9kry4RsKVCduWp82HkW6hhgi2unnvOAUS72t8/edit?usp=sharing > > In short, it: > - adds support for precise function reference with fully/partially > qualified name > - redefines function resolution order for ambiguous function reference > - adds support for Hive's rich built-in functions (support for Hive user > defined functions was already added in 1.9.0) > - clarifies the concept of temporary functions > > Would love to hear your thoughts. > > Bowen >
