From: Noah Misch <noah@leadboat.com>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: WAL-log inplace update before revealing it to other sessions.
Date: Wed, 17 Dec 2025 00:14:48 +0000
Message-ID: <E1vVfBn-0019OT-2A@gemulon.postgresql.org> (raw)
WAL-log inplace update before revealing it to other sessions.
A buffer lock won't stop a reader having already checked tuple
visibility. If a vac_update_datfrozenid() and then a crash happened
during inplace update of a relfrozenxid value, datfrozenxid could
overtake relfrozenxid. That could lead to "could not access status of
transaction" errors.
Back-patch to v14 - v17. This is a back-patch of commits:
- 8e7e672cdaa6bfec85d4d5dd9be84159df23bb41
(main change, on master, before v18 branched)
- 818013665259d4242ba641aad705ebe5a3e2db8e
(defect fix, on master, before v18 branched)
It reverses commit bc6bad88572501aecaa2ac5d4bc900ac0fd457d5, my revert
of the original back-patch.
In v14, this also back-patches the assertion removal from commit
7fcf2faf9c7dd473208fd6d5565f88d7f733782b.
Discussion: https://postgr.es/m/20240620012908.92.nmisch@google.com
Backpatch-through: 14-17
Branch
------
REL_14_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/e4b1986b9899fedc50c99738f85da39e65e4743f
Modified Files
--------------
src/backend/access/heap/README.tuplock | 4 +-
src/backend/access/heap/heapam.c | 68 ++++++++++++++++++++++++++-------
src/backend/access/transam/xloginsert.c | 2 -
3 files changed, 55 insertions(+), 19 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: noah@leadboat.com, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: WAL-log inplace update before revealing it to other sessions.
In-Reply-To: <E1vVfBn-0019OT-2A@gemulon.postgresql.org>
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