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Michael Paquier e063ccc722 Fix orphaned origin in shared memory after DROP SUBSCRIPTION 
Since ce0fdbfe97, a replication slot and an origin are created by each
tablesync worker, whose information is stored in both a catalog and
shared memory (once the origin is set up in the latter case).  The
transaction where the origin is created is the same as the one that runs
the initial COPY, with the catalog state of the origin becoming visible
for other sessions only once the COPY transaction has committed.  The
catalog state is coupled with a state in shared memory, initialized at
the same time as the origin created in the catalogs.  Note that the
transaction doing the initial data sync can take a long time, time that
depends on the amount of data to transfer from a publication node to its
subscriber node.

Now, when a DROP SUBSCRIPTION is executed, all its workers are stopped
with the origins removed.  The removal of each origin relies on a
catalog lookup.  A worker still running the initial COPY would fail its
transaction, with the catalog state of the origin rolled back while the
shared memory state remains around.  The session running the DROP
SUBSCRIPTION should be in charge of cleaning up the catalog and the
shared memory state, but as there is no data in the catalogs the shared
memory state is not removed.  This issue would leave orphaned origin
data in shared memory, leading to a confusing state as it would still
show up in pg_replication_origin_status.  Note that this shared memory
data is sticky, being flushed on disk in replorigin_checkpoint at
checkpoint.  This prevents other origins from reusing a slot position
in the shared memory data.

To address this problem, the commit moves the creation of the origin at
the end of the transaction that precedes the one executing the initial
COPY, making the origin immediately visible in the catalogs for other
sessions, giving DROP SUBSCRIPTION a way to know about it.  A different
solution would have been to clean up the shared memory state using an
abort callback within the tablesync worker.  The solution of this commit
is more consistent with the apply worker that creates an origin in a
short transaction.

A test is added in the subscription test 004_sync.pl, which was able to
display the problem.  The test fails when this commit is reverted.

Reported-by: Tenglong Gu <brucegu@amazon.com>
Reported-by: Daisuke Higuchi <higudai@amazon.com>
Analyzed-by: Michael Paquier <michael@paquier.xyz>
Author: Hou Zhijie <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/aUTekQTg4OYnw-Co@paquier.xyz
Backpatch-through: 14
2025-12-23 14:32:21 +09:00
config Don't put library-supplied -L/-I switches before user-supplied ones. 2025-07-29 15:17:41 -04:00
contrib Fix multibyte issue in ltree_strncasecmp(). 2025-12-16 10:36:29 -08:00
doc doc: Fix statement about ON CONFLICT and deferrable constraints. 2025-12-09 10:49:17 +00:00
src Fix orphaned origin in shared memory after DROP SUBSCRIPTION 2025-12-23 14:32:21 +09:00
.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 ci: Add missing "set -e" to scripts run by su. 2025-11-06 14:18:16 +13:00
.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 Align organization wording in copyright statement 2025-05-16 11:20:07 -04:00
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/.