Re: row filtering for logical replication

Greg Nancarrow <gregn4422@gmail.com>

From: Greg Nancarrow <gregn4422@gmail.com>
To: Euler Taveira <euler@eulerto.com>
Cc: Peter Smith <smithpb2250@gmail.com>, Amit Kapila <amit.kapila16@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: 2021-07-12T02:15:04Z
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 Mon, Jul 12, 2021 at 9:31 AM Euler Taveira <euler@eulerto.com> wrote:
>
> cfbot seems to be unhappy with v18 on some of the hosts. Cirrus/FreeBSD failed
> in the test 010_truncate. It also failed in a Cirrus/Linux box. I failed to
> reproduce in my local FreeBSD box. Since it passes appveyor and Cirrus/macos,
> it could probably be a transient issue.
>

I don't think it's a transient issue.
I also get a test failure in subscription/010_truncate.pl when I run
"make check-world" with the v18 patches applied.
The problem can be avoided with the following change (to match what
was originally in my v17-0005 performance-improvement patch):

diff --git a/src/backend/replication/pgoutput/pgoutput.c
b/src/backend/replication/pgoutput/pgoutput.c
index 08c018a300..800bae400b 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -1256,8 +1256,8 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
         }

         /* create a tuple table slot for row filter */
-        tupdesc = RelationGetDescr(relation);
         oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+        tupdesc = CreateTupleDescCopy(RelationGetDescr(relation));
         entry->scantuple = MakeSingleTupleTableSlot(tupdesc, &TTSOpsHeapTuple);
         MemoryContextSwitchTo(oldctx);

This creates a TupleDesc copy in CacheMemoryContext that is not
refcounted, so it side-steps the problem.
At this stage I am not sure why the original v18 patch code doesn't
work correctly for the TupleDesc refcounting here.
The TupleDesc refcount is zero when it's time to dealloc the tuple
slot (thus causing that Assert to fire), yet when the slot was
created, the TupleDesc refcount was incremented.- so it seems
something else has already decremented the refcount by the time it
comes to deallocate the slot. Perhaps there's an order-of-cleanup or
MemoryContext issue here or some buggy code somewhere, not sure yet.

Regards,
Greg Nancarrow
Fujitsu Australia