From: Andres Freund <andres@anarazel.de>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Avoid edge case in pg_visibility test with small shared_buffers
Date: Tue, 26 Mar 2024 03:28:23 +0000
Message-ID: <E1roxU6-005gkN-Vy@gemulon.postgresql.org> (raw)
Avoid edge case in pg_visibility test with small shared_buffers
Since 82a4edabd27 we can bulk extend relations. The bulk relation extension
logic has a heuristic component. Normally the heurstic does not trigger in the
occasionally-failing test case, as the relation is only extended once. But
with very small shared_buffers the limits for the number of buffers pinned at
once prevent the extension from happening at once. With the second "bulk"
extension, the heuristic kicks in, and the relation ends up one block bigger.
That's ok from a correctness perspective, but changes the results of the test
query due to one additional block.
We discussed a few more expansive fixes, but for now have decided to avoid
this by making the table a bit smaller.
Author: Heikki Linnakangas <hlinnaka@iki.fi>
Reported-by:
Discussion: https://postgr.es/m/29c74104-210b-ef39-2522-27a6aa7a704f@iki.fi
Discussion: https://postgr.es/m/20230916000011.2ugpkkkp7bpp4cfh@awork3.anarazel.de
Backpatch: 16-, where the new relation extension logic was added
Branch
------
REL_16_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/408209d6a9ae90a822edd48ce3c173b8b7e04ab7
Modified Files
--------------
contrib/pg_visibility/expected/pg_visibility.out | 3 +--
contrib/pg_visibility/sql/pg_visibility.sql | 6 ------
2 files changed, 1 insertion(+), 8 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: andres@anarazel.de, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Avoid edge case in pg_visibility test with small shared_buffers
In-Reply-To: <E1roxU6-005gkN-Vy@gemulon.postgresql.org>
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