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Michael Paquier 97b101776c Add pg_get_multixact_stats()
This new function exposes at SQL level some information related to
multixacts, not available until now.  This data is useful for monitoring
purposes, especially for workloads that make a heavy use of multixacts:
- num_mxids, number of MultiXact IDs in use.
- num_members, number of member entries in use.
- members_size, bytes used by num_members in pg_multixact/members/.
- oldest_multixact: oldest MultiXact still needed.

This patch has been originally proposed when MultiXactOffset was still
32 bits, to monitor wraparound.  This part is not relevant anymore since
bd8d9c9bdf that has widen MultiXactOffset to 64 bits.  The monitoring
of disk space usage for the members is still relevant.

Some tests are added to check this function, in the shape of one
isolation test with concurrent transactions that take a ROW SHARE lock,
and some SQL tests for pg_read_all_stats.  Some documentation is added
to explain some patterns that can come from the information provided by
the function.

Bump catalog version.

Author: Naga Appani <nagnrik@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Atsushi Torikoshi <torikoshia@oss.nttdata.com>
Discussion: https://postgr.es/m/CA+QeY+AAsYK6WvBW4qYzHz4bahHycDAY_q5ECmHkEV_eB9ckzg@mail.gmail.com
2025-12-30 15:38:50 +09:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Refactor static_assert() support. 2025-12-15 11:54:23 +01:00
contrib Further stabilize a postgres_fdw test case. 2025-12-29 12:53:49 -05:00
doc Add pg_get_multixact_stats() 2025-12-30 15:38:50 +09:00
src Add pg_get_multixact_stats() 2025-12-30 15:38:50 +09:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:34 -04:00
.cirrus.tasks.yml headerscheck ccache support 2025-12-04 11:23:23 +01:00
.cirrus.yml ci: Per-repo configuration for manually trigger tasks 2025-08-14 11:54:03 -04:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Update .editorconfig and .gitattributes for postgresql.conf.sample. 2025-11-18 10:28:36 -06:00
.git-blame-ignore-revs Add commit 86b276a4a9 to .git-blame-ignore-revs. 2025-12-05 14:21:12 -06:00
.gitattributes Update .editorconfig and .gitattributes for postgresql.conf.sample. 2025-11-18 10:28:36 -06:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
.mailmap Add a Git .mailmap file 2024-11-05 13:56:02 +01:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Refactor static_assert() support. 2025-12-15 11:54:23 +01:00
configure.ac Refactor static_assert() support. 2025-12-15 11:54:23 +01:00
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 Remove AIX support 2024-02-28 15:17:23 +04:00
meson.build Refactor static_assert() support. 2025-12-15 11:54:23 +01:00
meson_options.txt Add support for basic NUMA awareness 2025-04-07 23:08:17 +02:00
README.md Revise the style of a paragraph in README.md. 2024-03-21 10:16:41 -05:00

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/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/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/.