Horton

Re: row filtering for logical replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Ajin Cherian <itsajin@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Euler Taveira <euler@eulerto.com>, Peter Smith <smithpb2250@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>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Langote <amitlangote09@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-11-10T02:47:48Z
Lists: pgsql-hackers

Commits

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  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, Nov 9, 2021 at 2:22 PM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
> On Fri, Nov 5, 2021 4:49 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > On Fri, Nov 5, 2021 at 10:44 AM Peter Smith <smithpb2250@gmail.com> wrote:
> > >
> > > PSA new set of v37* patches.
> > 3.
> > - | ColId
> > + | ColId OptWhereClause
> >   {
> >   $$ = makeNode(PublicationObjSpec);
> >   $$->pubobjtype = PUBLICATIONOBJ_CONTINUATION;
> > - $$->name = $1;
> > + if ($2)
> > + {
> > + $$->pubtable = makeNode(PublicationTable); $$->pubtable->relation =
> > + makeRangeVar(NULL, $1, @1); $$->pubtable->whereClause = $2; } else {
> > + $$->name = $1; }
> >
> > Again this doesn't appear to be the right way. I think this should be handled at
> > a later point.
>
> I think the difficulty to handle this at a later point is that we need to make
> sure we don't lose the whereclause. Currently, we can only save the whereclause
> in PublicationTable structure and the PublicationTable is only used for TABLE,
> but '| ColId' can be used for either a SCHEMA or TABLE. We cannot distinguish
> the actual type at this stage, so we always need to save the whereclause if
> it's NOT NULL.
>

I see your point. But, I think we can add some comments here
indicating that the user might have mistakenly given where clause with
some schema which we will identify later and give an appropriate
error. Then, in preprocess_pubobj_list(), identify if the user has
given the where clause with schema name and give an appropriate error.

> I think the possible approaches to delay this check are:
>
> (1) we can delete the PublicationTable structure and put all the vars(relation,
> whereclause) in PublicationObjSpec. In this approach, we don't need check if
> the whereclause is NULL in the '| ColId', we can check this at a later point.
>

Yeah, we can do this but I don't think it will reduce any checks later
to identify if the user has given where clause only for tables. So,
let's keep this structure around as that will at least keep all things
related to the table together in one structure.

> Or
>
> (2) Add a new pattern for whereclause in PublicationObjSpec:
>
> The change could be:
>
> PublicationObjSpec:
> ...
> | ColId
>         ...
> + | ColId WHERE '(' a_expr ')'
> + {
> + $$ = makeNode(PublicationObjSpec);
> + $$->pubobjtype = PUBLICATIONOBJ_CONTINUATION;
> + $$->pubtable = makeNode(PublicationTable);
> + $$->pubtable->relation = makeRangeVar(NULL, $1, @1);
> + $$->pubtable->whereClause = $2;
> + }
>
> In this approach, we also don't need the "if ($2)" check.
>

This seems redundant and we still need same checks later to see if the
where clause is given with the table object.

-- 
With Regards,
Amit Kapila.