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Re: IPC/MultixactCreation on the Standby server

Dmitry <dsy.075@yandex.ru>

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From: Dmitry <dsy.075@yandex.ru>
To: Andrey Borodin <x4mmm@yandex-team.ru>, Álvaro Herrera <alvherre@kurilemu.de>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2025-07-29T07:17:42Z
Lists: pgsql-hackers 
I'll duplicate the message, the previous one turned out to have poor 
formatting, sorry.

On 28.07.2025 15:49, Andrey Borodin wrote:
> I also attach a version for PG17, maybe Dmitry could try to reproduce 
> the problem with this patch.
Andrey, thank you very much for your work, and also thanks to Álvaro for 
joining the discussion on the problem.
I ran tests on PG17 with patch v8, there are no more sessions hanging on 
the replica, great!

Replica requests are canceled with recovery conflicts.

ERROR: canceling statement due to conflict with recovery
DETAIL: User was holding shared buffer pin for too long.
STATEMENT: select sum(val) from tbl2;

or

ERROR: canceling statement due to conflict with recovery
DETAIL: User query might have needed to see row versions that must be 
removed.
STATEMENT: select sum(val) from tbl2;

But on the master, some of the requests then fail with an error, 
apparently invalid multixact's remain in the pages.

ERROR: MultiXact 81926 has invalid next offset
STATEMENT: select * from tbl2 where id = $1 for no key update;

ERROR: MultiXact 81941 has invalid next offset
CONTEXT: while scanning block 3 offset 244 of relation "public.tbl2" 
automatic vacuum of table "postgres.public.tbl2"

Best regards,
Dmitry.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix test to work with non-8kB block sizes

  2. Fix setting next multixid's offset at offset wraparound

  3. Add test for multixid wraparound

  4. Set next multixid's offset when creating a new multixid

  5. psql: Improve tab completion for large objects.

  6. Refactor some repetitive SLRU code

  7. Transaction IDs wrap around, per my proposal of 13-Aug-01. More