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Amit Kapila 3243c0177e Prevent invalidation of newly synced replication slots. 
A race condition could cause a newly synced replication slot to become
invalidated between its initial sync and the checkpoint.

When syncing a replication slot to a standby, the slot's initial
restart_lsn is taken from the publisher's remote_restart_lsn. Because slot
sync happens asynchronously, this value can lag behind the standby's
current redo pointer. Without any interlocking between WAL reservation and
checkpoints, a checkpoint may remove WAL required by the newly synced
slot, causing the slot to be invalidated.

To fix this, we acquire ReplicationSlotAllocationLock before reserving WAL
for a newly synced slot, similar to commit 006dd4b2e5. This ensures that
if WAL reservation happens first, the checkpoint process must wait for
slotsync to update the slot's restart_lsn before it computes the minimum
required LSN.

However, unlike in ReplicationSlotReserveWal(), this lock alone cannot
protect a newly synced slot if a checkpoint has already run
CheckPointReplicationSlots() before slotsync updates the slot. In such
cases, the remote restart_lsn may be stale and earlier than the current
redo pointer. To prevent relying on an outdated LSN, we use the oldest
WAL location available if it is greater than the remote restart_lsn.

This ensures that newly synced slots always start with a safe, non-stale
restart_lsn and are not invalidated by concurrent checkpoints.

Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Vitaly Davydov <v.davydov@postgrespro.ru>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Backpatch-through: 17
Discussion: https://postgr.es/m/TY4PR01MB16907E744589B1AB2EE89A31F94D7A%40TY4PR01MB16907.jpnprd01.prod.outlook.com
2026-01-27 05:49:23 +00:00
config Don't put library-supplied -L/-I switches before user-supplied ones. 2025-07-29 15:17:41 -04:00
contrib Fix bogus ctid requirement for dummy-root partitioned targets 2026-01-23 10:23:22 +09:00
doc doc: Mention pg_get_partition_constraintdef() 2026-01-22 16:35:48 +09:00
src Prevent invalidation of newly synced replication slots. 2026-01-27 05:49:23 +00:00
.abi-compliance-history Update .abi-compliance-history for PrepareToInvalidateCacheTuple(). 2025-12-17 09:48:56 -08:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:02:42 -04:00
.cirrus.tasks.yml Fix typo 2026-01-07 15:48:54 +01:00
.cirrus.yml ci: Per-repo configuration for manually trigger tasks 2025-08-14 11:33:47 -04:00
.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 previous commit to .git-blame-ignore-revs. 2025-10-21 10:02:19 -05:00
.gitattributes Fix git whitespace warning 2025-08-15 10:32:07 +02:00
.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 17.7. 2025-11-10 16:53:58 -05:00
configure.ac Stamp 17.7. 2025-11-10 16:53:58 -05:00
COPYRIGHT Update copyright for 2026 2026-01-01 13:24:10 -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 Add check for large files in meson.build 2025-11-12 09:02:32 +09:00
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

README.md

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/.