+1 to Jark's proposal
I like the difference between just loading and actually enabling these
modules.
@Rui: I would use the same behavior as catalogs here. You cannot `USE` a
catalog without creating it before.
Another question is whether a LOAD operation also adds the module to the
enabled list by default?
Regards,
Timo
On 01.02.21 13:52, Rui Li wrote:
If `USE MODULES` implies unloading modules that are not listed, does it
also imply loading modules that are not previously loaded, especially since
we're mapping modules by name now?
On Mon, Feb 1, 2021 at 8:20 PM Jark Wu <imj...@gmail.com> wrote:
I agree with Timo that the USE implies the specified modules are in use in
the specified order and others are not used.
This would be easier to know what's the result list and order after the USE
statement.
That means: if current modules in order are x, y, z. And `USE MODULES z, y`
means current modules in order are z, y.
But I would like to not unload the unmentioned modules in the USE
statement. Because it seems strange that USE
will implicitly remove modules. In the above example, the user may type the
wrong modules list using USE by mistake
and would like to declare the list again, the user has to create the
module again with some properties he may don't know. Therefore, I propose
the USE statement just specifies the current module lists and doesn't
unload modules.
Besides that, we may need a new syntax to list all the modules including
not used but loaded.
We can introduce SHOW FULL MODULES for this purpose with an additional
`used` column.
For example:
Flink SQL> list modules:
-----------
| modules |
-----------
| x |
| y |
| z |
-----------
Flink SQL> USE MODULES z, y;
Flink SQL> show modules:
-----------
| modules |
-----------
| z |
| y |
-----------
Flink SQL> show FULL modules;
-------------------
| modules | used |
-------------------
| z | true |
| y | true |
| x | false |
-------------------
Flink SQL> USE MODULES z, y, x;
Flink SQL> show modules;
-----------
| modules |
-----------
| z |
| y |
| x |
-----------
What do you think?
Best,
Jark
On Mon, 1 Feb 2021 at 19:02, Jane Chan <qingyue....@gmail.com> wrote:
Hi Timo, thanks for the discussion.
It seems to reach an agreement regarding #3 that <1> Module name should
better be a simple identifier rather than a string literal. <2> Property
`type` is redundant and should be removed, and mapping will rely on the
module name because loading a module multiple times just using a
different
module name doesn't make much sense. <3> We should migrate to the newer
API
rather than the deprecated `TableFactory` class.
Regarding #1, I think the point lies in whether changing the resolution
order implies an `unload` operation explicitly (i.e., users could sense
it). What do others think?
Best,
Jane
On Mon, Feb 1, 2021 at 6:41 PM Timo Walther <twal...@apache.org> wrote:
IMHO I would rather unload the not mentioned modules. The statement
expresses `USE` that implicilty implies that the other modules are "not
used". What do others think?
Regards,
Timo
On 01.02.21 11:28, Jane Chan wrote:
Hi Jark and Rui,
Thanks for the discussions.
Regarding #1, I'm fine with `USE MODULES` syntax, and
It can be interpreted as "setting the current order of modules",
which
is
similar to "setting the current catalog" for `USE CATALOG`.
I would like to confirm that the unmentioned modules remain in the
same
relative order? E.g., if there are three loaded modules `X`, `Y`,
`Z`,
then
`USE MODULES Y, Z` means shifting the order to `Y`, `Z`, `X`.
Regarding #3, I'm fine with mapping modules purely by name, and I
think
Jark raised a good point on making the module name a simple
identifier
instead of a string literal. For backward compatibility, since we
haven't
supported this syntax yet, the affected users are those who defined
modules
in the YAML configuration file. Maybe we can eliminate the 'type'
from
the
'requiredContext' to make it optional. Thus the proposed mapping
mechanism
could use the module name to lookup the suitable factory, and in the
meanwhile updating documentation to encourage users to simplify their
YAML
configuration. And in the long run, we can deprecate the 'type'.
Best,
Jane
On Mon, Feb 1, 2021 at 4:19 PM Rui Li <lirui.fu...@gmail.com> wrote:
Thanks Jane for starting the discussion.
Regarding #1, I also prefer `USE MODULES` syntax. It can be
interpreted
as
"setting the current order of modules", which is similar to "setting
the
current catalog" for `USE CATALOG`.
Regarding #3, I'm fine to map modules purely by name because I think
it
satisfies all the use cases we have at hand. But I guess we need to
make
sure we're backward compatible, i.e. users don't need to change
their
yaml
files to configure the modules.
On Mon, Feb 1, 2021 at 3:10 PM Jark Wu <imj...@gmail.com> wrote:
Thanks Jane for the summary and starting the discussion in the
mailing
list.
Here are my thoughts:
1) syntax to reorder modules
I agree with Rui Li it would be quite useful if we can have some
syntax
to
reorder modules.
I slightly prefer `USE MODULES x, y, z` than `RELOAD MODULES x, y,
z`,
because USE has a more sense of effective and specifying ordering,
than
RELOAD.
From my feeling, RELOAD just means we unregister and register
x,y,z
modules
again,
it sounds like other registered modules are still in use and in the
order.
3) mapping modules purely by name
This can definitely improve the usability of loading modules,
because
the 'type=' property
looks really redundant. We can think of this as a syntax sugar that
the
default type value is the module name.
And we can support to specify 'type=' property in the future to
allow
multiple modules for one module type.
Besides, I would like to mention one more change, that the module
name
proposed in FLIP-68 is a string literal.
But I think we are all on the same page to change it into a simple
(non-compound) identifier.
LOAD/UNLOAD MODULE 'core'
==>
LOAD/UNLOAD MODULE core
Best,
Jark
On Sat, 30 Jan 2021 at 04:00, Jane Chan <qingyue....@gmail.com>
wrote:
Hi everyone,
I would like to start a discussion on FLINK-21045 [1] about
supporting
`LOAD MODULE` and `UNLOAD MODULE` SQL syntax. It's first proposed
by
FLIP-68 [2] as following.
-- load a module with the given name and append it to the end of
the
module
list
LOAD MODULE 'name' [WITH ('type'='xxx', 'prop'='myProp', ...)]
--unload a module by name from the module list and other modules
remain
in
the same relative positions
UNLOAD MODULE 'name'
After a round of discussion on the Jira ticket, it seems some
unanswered
questions need more opinions and suggestions.
1. The way to redefine resolution order easily
Rui Li suggested introducing `USE MODULES` and adding similar
functionality to the API because
1) It's very tedious to unload old modules just to reorder
them.
2) Users may not even know how to "re-load" an old module if it
was
not
initially loaded by the user, e.g. don't know which type to use.
Jane Chan wondered that module is not like the catalog which
has
a
concept of namespace could specify, and `USE` sounds like a
mutual-exclusive concept.
Maybe `RELOAD MODULES` can express upgrading the priority of
the
loaded
module(s).
2. `LOAD/UNLOAD MODULE` v.s. `CREATE/DROP MODULE` syntax
Jark Wu and Nicholas Jiang proposed to use `CREATE/DROP
MODULE`
instead
of `LOAD/UNLOAD MODULE` because
1) From a pure SQL user's perspective, maybe `CREATE MODULE +
USE
MODULE`
is easier to use rather than `LOAD/UNLOAD`.
2) This will be very similar to what the catalog used now.
Timo Walther would rather stick to the agreed design because
loading/unloading modules is a concept known from kernels etc.
3. Simplify the module design by mapping modules purely by name
LOAD MODULE geo_utils
LOAD MODULE hive WITH ('version'='2.1') -- no dedicated
'type='/'module='
but allow only 1 module to be loaded parameterized
UNLOAD hive
USE MODULES hive, core
Please find more details in the reference link. Looking forward to
your
feedback.
[1] https://issues.apache.org/jira/browse/FLINK-21045#
<
https://cwiki.apache.org/confluence/display/FLINK/FLIP-68%3A+Extend+Core+Table+System+with+Pluggable+Modules
[2]
https://cwiki.apache.org/confluence/display/FLINK/FLIP-68%3A+Extend+Core+Table+System+with+Pluggable+Modules
Best,
Jane
--
Best regards!
Rui Li
