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Re: Column Filtering in Logical Replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Justin Pryzby <pryzby@telsasoft.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Smith <smithpb2250@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>
Date: 2022-03-24T02:58:25Z
Lists: pgsql-hackers 
On Thu, Mar 24, 2022 at 4:11 AM Tomas Vondra
<tomas.vondra@enterprisedb.com> wrote:
>
> On 3/21/22 12:28, Amit Kapila wrote:
> > On Fri, Mar 18, 2022 at 8:13 PM Tomas Vondra
> > <tomas.vondra@enterprisedb.com> wrote:
> >>
> >> Ah, thanks for reminding me - it's hard to keep track of all the issues
> >> in threads as long as this one.
> >>
> >> BTW do you have any opinion on the SET COLUMNS syntax? Peter Smith
> >> proposed to get rid of it in [1] but I'm not sure that's a good idea.
> >> Because if we ditch it, then removing the column list would look like this:
> >>
> >>     ALTER PUBLICATION pub ALTER TABLE tab;
> >>
> >> And if we happen to add other per-table options, this would become
> >> pretty ambiguous.
> >>
> >> Actually, do we even want to allow resetting column lists like this? We
> >> don't allow this for row filters, so if you want to change a row filter
> >> you have to re-add the table, right?
> >>
> >
> > We can use syntax like: "alter publication pub1 set table t1 where (c2
> >> 10);" to reset the existing row filter. It seems similar thing works
> > for column list as well ("alter publication pub1 set table t1 (c2)
> > where (c2 > 10)"). If I am not missing anything, I don't think we need
> > additional Alter Table syntax.
> >
> >> So maybe we should just ditch ALTER
> >> TABLE entirely.
> >>
> >
> > Yeah, I agree especially if my above understanding is correct.
> >
>
> I think there's a gotcha that
>
>    ALTER PUBLICATION pub SET TABLE t ...
>
> also removes all other relations from the publication, and it removes
> and re-adds the table anyway. So I'm not sure what's the advantage?
>

I think it could be used when the user has fewer tables and she wants
to change the list of published tables or their row/column filters. I
am not sure of the value of this to users but this was a pre-existing
syntax.

> Anyway, I don't see why we would need such ALTER TABLE only for column
> filters and not for row filters - either we need to allow this for both
> options or none of them.
>

+1. I think for now we can leave this new ALTER TABLE syntax and do it
for both column and row filters together.


-- 
With Regards,
Amit Kapila.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Doc: Explain about Column List feature.

  2. Doc: fix column list vs. replica identity rules.

  3. Prohibit combining publications with different column lists.

  4. Fix the check to limit sync workers.

  5. Wait for subscription to sync in t/031_column_list.sql

  6. Move prattrs to the pg_publication_rel section in docs

  7. Allow specifying column lists for logical replication

  8. Fix row filters with multiple publications

  9. Fix publish_as_relid with multiple publications

  10. Add some additional tests for row filters in logical replication.

  11. Add index on pg_publication_rel.prpubid

  12. Avoid using DefElemAction in AlterPublicationStmt

  13. Small cleanups related to PUBLICATION framework code

  14. Add PublicationTable and PublicationRelInfo structs

  15. Fix various concurrency issues in logical replication worker launching