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help / color / mirror / Atom feedFrom: Peter Geoghegan <pg@bowt.ie>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Move visibility map memory ordering comments.
Date: Thu, 03 Sep 2026 19:36:43 +0000
Message-ID: <E1x2DEo-00000003Lvo-01Xg@gemulon.postgresql.org> (raw)
Move visibility map memory ordering comments.
nodeIndexonlyscan.c has long carried a detailed explanation of why it is
safe for index-only scans to test a visibility map bit without locking
the visibility map buffer, despite the possibility of reading a stale
value. Move that explanation into visibilitymap.c.
This is preparation for an upcoming commit that will move VM checks
needed by index-only scans out of the executor and into heapam.
Author: Peter Geoghegan <pg@bowt.ie>
Suggested-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://postgr.es/m/t6mtqbv2mbfhjni4bvwdgoecppjmxvbyfwl6utovzv76xc2672%40k3o5ryevaeqv
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/903d9d12cc0adcd9a7f92c7b35333e9e40756fbf
Modified Files
--------------
src/backend/access/heap/visibilitymap.c | 27 ++++++++++++++++++++++++++-
src/backend/executor/nodeIndexonlyscan.c | 29 ++++-------------------------
2 files changed, 30 insertions(+), 26 deletions(-)
Message-ID: <E1x2DEo-00000003Lvo-01Xg@gemulon.postgresql.org>
Permalink: ../E1x2DEo-00000003Lvo-01Xg@gemulon.postgresql.org/
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To: pgsql-committers@postgresql.org
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Subject: Re: pgsql: Move visibility map memory ordering comments.
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