Re: Regression tests failures due to concurrent grants

From: Alexander Lakhin <exclusion(at)gmail(dot)com>
To: Jeff Davis <pgsql(at)j-davis(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org
Cc: Jeff Davis <jdavis(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Noah Misch <noah(at)leadboat(dot)com>
Subject: Re: Regression tests failures due to concurrent grants
Date: 2026-09-19 13:00:00
Message-ID: 7ef72f67-6ed0-4197-96ac-284aff267079@gmail.com
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Hello Andres and Jeff,

18.09.2026 21:08, Jeff Davis wrote:
> On Fri, 2026-09-18 at 12:56 -0400, Andres Freund wrote:
>> To do better, we would need to use a
>>  * self-exclusive lock, perhaps ShareUpdateExclusiveLock, here and
>> before
>>  * *every* CatalogTupleUpdate() of a row that GRANT/REVOKE can
>> affect.
> ...
>> I also am not convinced that cancelling autovacs in response to a
>> command like
>> this would be the end of the world.
> For GRANT/REVOKE, that matches my intuition. But if we need a stronger
> lock before every modification of a catalog row, that's a larger change
> that would affect lots of DDL.

I've recalled a known issue (still reproduced on current master) with
VACUUM and GRANT locks, which might be interesting to you in this context:
https://www.postgresql.org/message-id/9f7cc148-55d1-4062-8229-b6886d7aa380%40gmail.com

Best regards,
Alexander

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