Hi Timo, Thanks for the FLIP. I also tend to think that Option 3 is better.
I would be also interested in a question mentioned by Benchao Li. And a similar question about nested queries like `SELECT * FROM (SELECT $rowtime, * FROM t);` Am I right that it will show `$rowtime` in output ? On Thu, Jul 27, 2023 at 6:58 AM Benchao Li <[email protected]> wrote: > Hi Timo, > > Thanks for the FLIP, I also like the idea and option 3 sounds good to me. > > I would like to discuss a case which is not mentioned in the current FLIP. > How are the "System column"s expressed in intermediate result, e.g. Join? > E.g. `SELECT * FROM t1 JOIN t2`, I guess it should not include "system > columns" from t1 and t2 as you proposed, and for `SELECT t1.$rowtime, * > FROM t1 JOIN t2`, it should also be valid. > Then the question is how to you plan to implement the "system columns", do > we need to add it to `RelNode` level? Or we just need to do it in the > parsing/validating phase? > I'm not sure that Calcite's "system column" feature is fully ready for this > since the code about this part is imported from the earlier project before > it gets into Apache, and has not been considered much in the past > development. > > > Jing Ge <[email protected]> 于2023年7月26日周三 00:01写道： > > > Hi Timo, > > > > Thanks for your proposal. It is a very pragmatic feature. Among all > options > > in the FLIP, option 3 is one I prefer too and I'd like to ask some > > questions to understand your thoughts. > > > > 1. I did some research on pseudo columns, just out of curiosity, do you > > know why most SQL systems do not need any prefix with their pseudo > column? > > 2. Some platform providers will use ${variable_name} to define their own > > configurations and allow them to be embedded into SQL scripts. Will there > > be any conflict with option 3? > > > > Best regards, > > Jing > > > > On Tue, Jul 25, 2023 at 7:00 PM Konstantin Knauf <[email protected]> > > wrote: > > > > > Hi Timo, > > > > > > this makes sense to me. Option 3 seems reasonable, too. > > > > > > Cheers, > > > > > > Konstantin > > > > > > Am Di., 25. Juli 2023 um 12:53 Uhr schrieb Timo Walther < > > > [email protected] > > > >: > > > > > > > Hi everyone, > > > > > > > > I would like to start a discussion about introducing the concept of > > > > "System Columns" in SQL and Table API. > > > > > > > > The subject sounds bigger than it actually is. Luckily, Flink SQL > > > > already exposes the concept of metadata columns. And this proposal is > > > > just a slight adjustment for how metadata columns can be used as > system > > > > columns. > > > > > > > > The biggest problem of metadata columns currently is that a catalog > > > > implementation can't provide them by default because they would > affect > > > > `SELECT *` when adding another one. > > > > > > > > Looking forward to your feedback on FLIP-348: > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-348%3A+Support+System+Columns+in+SQL+and+Table+API > > > > > > > > Thanks, > > > > Timo > > > > > > > > > > > > > -- > > > https://twitter.com/snntrable > > > https://github.com/knaufk > > > > > > > > -- > > Best, > Benchao Li > -- Best regards, Sergey
