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Heikki Linnakangas 302ce5bd93 Fix rare assertion failure in standby, if primary is restarted
During hot standby, ExpireAllKnownAssignedTransactionIds() and
ExpireOldKnownAssignedTransactionIds() functions mark old transactions
as no-longer running, but they failed to update xactCompletionCount
and latestCompletedXid. AFAICS it would not lead to incorrect query
results, because those functions effectively turn in-progress
transactions into aborted transactions and an MVCC snapshot considers
both as "not visible". But it could surprise GetSnapshotDataReuse()
and trigger the "TransactionIdPrecedesOrEquals(TransactionXmin,
RecentXmin))" assertion in it, if the apparent xmin in a backend would
move backwards. We saw this happen when GetCatalogSnapshot() would
reuse an older catalog snapshot, when GetTransactionSnapshot() had
already advanced TransactionXmin.

The bug goes back all the way to commit 623a9ba79b in v14 that
introduced the snapshot reuse mechanism, but it started to happen more
frequently with commit 952365cded which removed a
GetTransactionSnapshot() call from backend startup. That made it more
likely for ExpireOldKnownAssignedTransactionIds() to be called between
GetCatalogSnapshot() and the first GetTransactionSnapshot() in a
backend.

Andres Freund first spotted this assertion failure on buildfarm member
'skink'. Reproduction and analysis by Tomas Vondra.

Backpatch-through: 14
Discussion: https://www.postgresql.org/message-id/oey246mcw43cy4qw2hqjmurbd62lfdpcuxyqiu7botx3typpax%40h7o7mfg5zmdj
2025-03-23 20:41:52 +02:00
config jit: Remove {llvm-config,clang}-N configure probes. 2024-05-16 13:58:25 +12:00
contrib Handle default NULL insertion a little better. 2025-01-29 15:31:55 -05:00
doc doc: Remove incorrect description about dropping replication slots. 2025-03-21 12:58:43 +09:00
src Fix rare assertion failure in standby, if primary is restarted 2025-03-23 20:41:52 +02:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml ci: Upgrade FreeBSD image 2025-03-05 10:29:08 -05:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add commit 7229ebe011 to .git-blame-ignore-revs. 2024-09-14 20:17:30 +02:00
.gitattributes Exclude LLVM files from whitespace checks 2024-11-27 11:09:27 +01:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Stamp 17.4. 2025-02-17 16:11:21 -05:00
configure.ac Stamp 17.4. 2025-02-17 16:11:21 -05:00
COPYRIGHT Update copyright for 2025 2025-01-01 11:21:54 -05:00
GNUmakefile.in Allow selecting the git revision to be packaged by "make dist". 2024-05-03 11:08:50 -04:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Adapt REL_17_STABLE to its new status as a stable branch 2024-07-01 08:05:35 +09:00
meson.build Make test portlock logic work with meson 2025-02-21 11:25:48 -05:00
meson_options.txt Allow selecting the git revision to be packaged by "make dist". 2024-05-03 11:08:50 -04:00
README.md Adapt REL_17_STABLE to its new status as a stable branch 2024-07-01 08:05:35 +09:00

PostgreSQL Database Management System

This directory contains the source code distribution of the PostgreSQL database management system.

PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.

Copyright and license information can be found in the file COPYRIGHT.

General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/17/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/17/installation.html.

The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.