From: Melanie Plageman <melanieplageman@gmail.com>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Test that vacuum removes tuples older than OldestXmin
Date: Tue, 24 Jun 2025 13:29:44 +0000
Message-ID: <E1uU3ia-0038Ns-2E@gemulon.postgresql.org> (raw)
Test that vacuum removes tuples older than OldestXmin
If vacuum fails to prune a tuple killed before OldestXmin, it will
decide to freeze its xmax and later error out in pre-freeze checks.
Add a test reproducing this scenario to the recovery suite which creates
a table on a primary, updates the table to generate dead tuples for
vacuum, and then, during the vacuum, uses a replica to force
GlobalVisState->maybe_needed on the primary to move backwards and
precede the value of OldestXmin set at the beginning of vacuuming the
table.
This test is coverage for a case fixed in 83c39a1f7f3. The test was
originally committed to master in aa607980aee but later reverted in
efcbb76efe4 due to test instability.
The test requires multiple index passes. In Postgres 17+, vacuum uses a
TID store for the dead TIDs that is very space efficient. With the old
minimum maintenance_work_mem of 1 MB, it required a large number of dead
rows to generate enough dead TIDs to force multiple index
vacuuming passes. Once the source code changes were made to allow a
minimum maintenance_work_mem value of 64kB, the test could be made much
faster and more stable.
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAAKRu_ZJBkidusDut6i%3DbDCiXzJEp93GC1%2BNFaZt4eqanYF3Kw%40mail.gmail.com
Backpatch-through: 17
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/303ba0573ce656b98620133cd17418dcd217318f
Modified Files
--------------
src/test/recovery/meson.build | 3 +-
src/test/recovery/t/048_vacuum_horizon_floor.pl | 278 ++++++++++++++++++++++++
2 files changed, 280 insertions(+), 1 deletion(-)
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To: pgsql-committers@postgresql.org
Cc: melanieplageman@gmail.com, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Test that vacuum removes tuples older than OldestXmin
In-Reply-To: <E1uU3ia-0038Ns-2E@gemulon.postgresql.org>
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