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help / color / mirror / Atom feedFrom: Fujii Masao <fujii@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix unlogged sequence corruption after standby promotion
Date: Mon, 29 Jun 2026 23:54:19 +0000
Message-ID: <E1weLnw-000iFs-06@gemulon.postgresql.org> (raw)
Fix unlogged sequence corruption after standby promotion
Previously, if an unlogged sequence was created on the primary and
replicated to a standby, reading the sequence after promoting the
standby (for example, with nextval()) could trigger the following
assertion failure:
TRAP: failed Assert("((const PageHeaderData *) page)->pd_special >= SizeOfPageHeaderData")
In non-assert builds, the same operation could instead fail with an
error such as:
ERROR: bad magic number in sequence
The problem was that seq_redo() updated the init fork page in shared
buffers but did not flush it to disk. During promotion,
ResetUnloggedRelations() recreates the main fork of unlogged
relations by copying the init fork from disk, bypassing shared
buffers. As a result, the main fork could be recreated from a stale
init fork instead of the WAL-replayed page.
Fix this by introducing a helper to flush init fork buffers
immediately, and make seq_redo() use it. As a result, the main fork
of an unlogged sequence is recreated from the up-to-date init fork on
disk, allowing the unlogged sequence to be read successfully after
standby promotion.
Backpatch to v15, where unlogged sequences were introduced.
Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwH1Ssze3XM6wjoTjSLVOR041c6xP+vsdLP951=w8oG8bA@mail.gmail.com
Backpatch-through: 15
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/a1ed6a9a031af5d945dee498ba364cddea7af59f
Modified Files
--------------
src/backend/access/hash/hash_xlog.c | 29 ++----------------
src/backend/access/transam/xlogutils.c | 26 ++++++++++++++++-
src/backend/commands/sequence.c | 1 +
src/include/access/xlogutils.h | 2 ++
src/test/recovery/meson.build | 1 +
.../recovery/t/054_unlogged_sequence_promotion.pl | 34 ++++++++++++++++++++++
6 files changed, 66 insertions(+), 27 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: fujii@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix unlogged sequence corruption after standby promotion
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