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
> > > >>
> > > >
> > >
> > >
> >
>
--
Best regards!
Rui Li
