Re: row filtering for logical replication

Amit Kapila <amit.kapila16@gmail.com>

From: Amit Kapila <amit.kapila16@gmail.com>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Ajin Cherian <itsajin@gmail.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Euler Taveira <euler@eulerto.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Önder Kalacı <onderkalaci@gmail.com>, japin <japinli@hotmail.com>, Michael Paquier <michael@paquier.xyz>, David Steele <david@pgmasters.net>, Craig Ringer <craig@2ndquadrant.com>, Amit Langote <amitlangote09@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-12-08T05:24:47Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →
  1. Release cache tuple when no longer needed

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

  3. Fix one of the tests introduced in commit 52e4f0cd47.

  4. Allow specifying row filters for logical replication of tables.

  5. Move scanint8() to numutils.c

  6. Replace Test::More plans with done_testing

  7. Reduce relcache access in WAL sender streaming logical changes

  8. Small cleanups related to PUBLICATION framework code

  9. Add a view to show the stats of subscription workers.

  10. Allow publishing the tables of schema.

  11. Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.

  12. Add PublicationTable and PublicationRelInfo structs

  13. Remove unused argument "txn" in maybe_send_schema().

  14. Add prepare API support for streaming transactions in logical replication.

  15. Unify PostgresNode's new() and get_new_node() methods

  16. Use l*_node() family of functions where appropriate

  17. Add support for prepared transactions to built-in logical replication.

  18. Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.

  19. Rename a parse node to be more general

  20. Remove unused column atttypmod from initial tablesync query

  21. SEARCH and CYCLE clauses

On Tue, Dec 7, 2021 at 6:31 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> On Tue, Dec 7, 2021 at 12:18 PM tanghy.fnst@fujitsu.com
> <tanghy.fnst@fujitsu.com> wrote:
> >
> > I have another problem with your patch. The document says:
> >
> > ... If the subscription has several publications in
> > +   which the same table has been published with different filters, those
> > +   expressions get OR'ed together so that rows satisfying any of the expressions
> > +   will be replicated. Notice this means if one of the publications has no filter
> > +   at all then all other filters become redundant.
> >
> > Then, what if one of the publications is specified as 'FOR ALL TABLES' or 'FOR
> > ALL TABLES IN SCHEMA'.
> >
> > For example:
> > create table tbl (a int primary key);"
> > create publication p1 for table tbl where (a > 10);
> > create publication p2 for all tables;
> > create subscription sub connection 'dbname=postgres port=5432' publication p1, p2;
>
> Thanks for the example. I was wondering about this case myself.
>

I think we should handle this case.

> >
> > I think for "FOR ALL TABLE" publication(p2 in my case), table tbl should be
> > treated as no filter, and table tbl should have no filter in subscription sub. Thoughts?
> >
> > But for now, the filter(a > 10) works both when copying initial data and later changes.
> >
> > To fix it, I think we can check if the table is published in a 'FOR ALL TABLES'
> > publication or published as part of schema in function pgoutput_row_filter_init
> > (which was introduced in v44-0003 patch), also we need to make some changes in
> > tablesync.c.
>
> In order to check "FOR ALL_TABLES", we might need to fetch publication
> metadata.
>

Do we really need to perform a separate fetch for this? In
get_rel_sync_entry(), we already have this information, can't we
someway stash that in the corresponding RelationSyncEntry so that same
can be used later for row filtering.

> Instead of that can we add a "TRUE" filter on all the tables
> which are part of FOR ALL TABLES publication?
>

How? We won't have an entry for such tables in pg_publication_rel
where we store row_filter information.

-- 
With Regards,
Amit Kapila.