RE: row filtering for logical replication

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

From: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: Amit Kapila <amit.kapila16@gmail.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: 2021-11-09T08:52:28Z
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, 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 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.

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.

What do you think ?

Best regards,
Hou zj