From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix bug in following update chain when locking a heap tuple
Date: Tue, 23 Dec 2025 12:07:33 +0000
Message-ID: <E1vY1Aq-002FRL-2U@gemulon.postgresql.org> (raw)
Fix bug in following update chain when locking a heap tuple
After waiting for a concurrent updater to finish, heap_lock_tuple()
followed the update chain to lock all tuple versions. However, when
stepping from the initial tuple to the next one, it failed to check
that the next tuple's XMIN matches the initial tuple's XMAX. That's an
important check whenever following an update chain, and the recursive
part that follows the chain did it, but the initial step missed it.
Without the check, if the updating transaction aborts, the updated
tuple is vacuumed away and replaced by an unrelated tuple, the
unrelated tuple might get incorrectly locked.
Author: Jasper Smit <jasper.smit@servicenow.com>
Discussion: https://www.postgresql.org/message-id/CAOG+RQ74x0q=kgBBQ=mezuvOeZBfSxM1qu_o0V28bwDz3dHxLw@mail.gmail...
Backpatch-through: 14
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/bb87d7fef1031b03e7595c05ef83f38d1df29028
Modified Files
--------------
src/backend/access/heap/heapam.c | 48 ++++++---
src/test/modules/injection_points/Makefile | 4 +-
.../injection_points/expected/heap_lock_update.out | 83 +++++++++++++++
src/test/modules/injection_points/meson.build | 1 +
.../injection_points/specs/heap_lock_update.spec | 117 +++++++++++++++++++++
5 files changed, 237 insertions(+), 16 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: heikki.linnakangas@iki.fi, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix bug in following update chain when locking a heap tuple
In-Reply-To: <E1vY1Aq-002FRL-2U@gemulon.postgresql.org>
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