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Subject: Re: Possible G2-item at SERIALIZABLE
From: Andrey Borodin <x4mmm@yandex-team.ru>
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 <CAN4CZFOKnrRdHfd_SKcaNT33iV-QvLYyvUnO5aM2nuUipnug6A@mail.gmail.com>
Date: Tue, 2 Jun 2026 13:18:29 +0500
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
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To: Zsolt Parragi <zsolt.parragi@percona.com>
Archived-At: 
 <https://www.postgresql.org/message-id/92417390-9753-4F6D-AE30-DA10FFF2A4DA%40yandex-team.ru>
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> On 2 Jun 2026, at 03:00, Zsolt Parragi <zsolt.parragi@percona.com> =
wrote:
>=20
> + /*
> +  * Mark ourselves doomed before raising the error.  Otherwise a
> +  * subtransaction abort (ROLLBACK TO SAVEPOINT) could swallow this
> +  * error and let the transaction commit anyway, defeating SSI.
> +  */
> + MySerializableXact->flags |=3D SXACT_FLAG_DOOMED;
> LWLockRelease(SerializableXactHashLock);
> ereport(ERROR,
> (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
>=20
> I wonder if it would make sense to introduce a
> "DoomMyselfAndRaiseSerializationFailure" helper for this, while fixing
> all occurrences we can find? That would make it more explicit, and
> also less repeated.
>=20
>> PFA attached isolation tester and hand-wavy fix. But I suspect there =
are more G-items
>> around.
>=20
> There are at least 2 more reproducible with the isolation tester in
> CheckForSerializableConflictOut ("conflict out to old pivot %u", and
> "conflict out to old committed transaction %u" directly below it).
> Probably "Canceled on conflict out to old pivot." also should have the
> same changes?

Thanks for looking into this!
I agree fix needs some refinement and can be improved.

However, let's settle on the bug first.
Do you think that recovering serialization error with ROLLBACK TO =
SAVEPOINT is a bug?

Honestly, I'm not entirely convinced myself. AFAIU SSI docs do not =
describe this case
clearly.


Best regards, Andrey Borodin.=