Re: IPC/MultixactCreation on the Standby server

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.