Horton

Re: row filtering for logical replication

Greg Nancarrow <gregn4422@gmail.com>

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From: Greg Nancarrow <gregn4422@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Peter Smith <smithpb2250@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, Euler Taveira <euler@eulerto.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: 2022-01-24T04:59:27Z
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 Mon, Jan 24, 2022 at 2:47 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> > (3) pgoutput_row_filter_exec_expr
> > pgoutput_row_filter_exec_expr() returns false if "isnull" is true,
> > otherwise (if "isnull" is false) returns the value of "ret"
> > (true/false).
> > So the following elog needs to be changed (Peter Smith previously
> > pointed this out, but it didn't get completely changed):
> >
> > BEFORE:
> > + elog(DEBUG3, "row filter evaluates to %s (isnull: %s)",
> > + DatumGetBool(ret) ? "true" : "false",
> > + isnull ? "true" : "false");
> > AFTER:
> > + elog(DEBUG3, "row filter evaluates to %s (isnull: %s)",
> > + isnull ? "false" : DatumGetBool(ret) ? "true" : "false",
> > + isnull ? "true" : "false");
> >
>
> Do you see any problem with the current? I find the current one easy
> to understand.
>

Yes, I see a problem. The logging doesn't match what the function code
actually returns when "isnull" is true.
When "isnull" is true, the function always returns false, not the
value of "ret".
For the current logging code to be correct, and match the function
return value, we should be able to change:

  if (isnull)
    return false;

to:

  if (isnull)
    return ret;

But regression tests fail when that code change is made (indicating
that there are cases when "isnull" is true but the function returns
true instead of false).
So the current logging code is NOT correct, and needs to be updated as
I indicated.


Regards,
Greg Nancarrow
Fujitsu Australia