Horton

Re: row filtering for logical replication

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, Euler Taveira <euler@eulerto.com>, Greg Nancarrow <gregn4422@gmail.com>, vignesh C <vignesh21@gmail.com>, Ajin Cherian <itsajin@gmail.com>, Dilip Kumar <dilipbalaut@gmail.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: 2022-01-24T05:53:59Z
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 Fri, Jan 21, 2022 at 2:04 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Thu, Jan 20, 2022 at 7:56 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > > >  Maybe this was meant to be "validate RF
> > > > expressions" and return, perhaps, a bitmapset of all invalid columns
> > > > referenced?
> > >
> > > Currently, we stop as soon as we find the first invalid column.
> >
> > That seems quite strange.  (And above you say "gather as much info as
> > possible", so why stop at the first one?)
> >
>
> Because that is an error case, so, there doesn't seem to be any
> benefit in proceeding further. However, we can build all the required
> information by processing all publications (aka gather all
> information) and then later give an error if that idea appeals to you
> more.
>
> > > >  (What is an invalid column in the first place?)
> > >
> > > A column that is referenced in the row filter but is not part of
> > > Replica Identity.
> >
> > I do wonder how do these invalid columns reach the table definition in
> > the first place.  Shouldn't these be detected at DDL time and prohibited
> > from getting into the definition?
> >
>
> As mentioned by Peter E [1], there are two ways to deal with this: (a)
> The current approach is that the user can set the replica identity
> freely, and we decide later based on that what we can replicate (e.g.,
> no updates). If we follow the same approach for this patch, we don't
> restrict what columns are part of the row filter, but we check what
> actions we can replicate based on the row filter. This is what is
> currently followed in the patch. (b) Add restrictions during DDL which
> is not as straightforward as it looks.

FYI - I also wanted to highlight that doing the replica identity
validation at update/delete time is not only following the "current
approach", as mentioned above, but this is also consistent with the
*documented* behaviour in PG docs (See [1] since PG v10),

<QUOTE>
If a table without a replica identity is added to a publication that
replicates UPDATE or DELETE operations then subsequent UPDATE or
DELETE operations will cause an error on the publisher.
</QUOTE>

Specifically,

It does *not* say that the RI validation error will happen when a
table is added to the publication at CREATE/ALTER PUBLICATION time.

It says that *subsequent* "UPDATE or DELETE operations will cause an error".

~~

The point is that it is one thing to decide to change something that
was never officially documented, but to change already *documented*
behaviour is much more radical and has the potential to upset some
users.

------
[1] https://www.postgresql.org/docs/devel/logical-replication-publication.

Kind Regards,
Peter Smith.
Fujitsu Australia