Re: Possible G2-item at SERIALIZABLE

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Kyle Kingsbury <aphyr(at)aphyr(dot)com>
Cc: PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>, samokhvalov(at)gmail(dot)com, Kirk Wolak <wolakk(at)gmail(dot)com>
Subject: Re: Possible G2-item at SERIALIZABLE
Date: 2026-05-30 18:47:00
Message-ID: 1F2F4318-437C-4AE1-8413-F94FBDD5AB68@yandex-team.ru
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> On 22 May 2026, at 21:44, Kyle Kingsbury <aphyr(at)aphyr(dot)com> wrote:
>
> If y'all have any luck reproducing this, I'd love to hear about it!

It looks like I've reproduced something similar with savepoints on HEAD and
REL_18_STABLE. I can't tell if it's really all what you observe. But, probably, part of it.

If that error is raised inside a subtransaction, ROLLBACK TO SAVEPOINT swallows it
and the transaction is free to COMMIT, defeating serializable isolation.

I did not try beyond 18, but I think it always has been there.

PFA attached isolation tester and hand-wavy fix. But I suspect there are more G-items
around.

Full Jepsen test you proposed is currently tried by Nik's machines(in cc).

Best regards, Andrey Borodin.

Attachment Content-Type Size
v1-0001-Add-isolation-test-SSI-serialization-failure-swal.patch application/octet-stream 4.2 KB
v1-0002-Doom-serializable-transaction-before-raising-seri.patch application/octet-stream 2.5 KB

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