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Peter Geoghegan 8a879119a1 Use fake LSNs to improve nbtree dropPin behavior. 
Use fake LSNs in all nbtree critical sections that write a WAL record.
That way we can safely apply the _bt_killitems LSN trick with logged and
unlogged indexes alike.  This brings the same benefits to plain scans of
unlogged relations that commit 2ed5b87f brought to plain scans of logged
relations: scans will drop their leaf page pin eagerly (by applying the
"dropPin" optimization), which avoids blocking progress by VACUUM.  This
is particularly helpful with applications that allow a scrollable cursor
to remain idle for long periods.

Preparation for an upcoming commit that will add the amgetbatch
interface, and switch nbtree over to it (from amgettuple) to enable I/O
prefetching.  The index prefetching read stream's effective prefetch
distance is adversely affected by any buffer pins held by the index AM.
At the same time, it can be useful for prefetching to read dozens of
leaf pages ahead of the scan to maintain an adequate prefetch distance.

The index prefetching patch avoids this tension by always eagerly
dropping index page pins of the kind traditionally held as an interlock
against unsafe concurrent TID recycling by VACUUM (essentially the same
way that amgetbitmap routines have always avoided holding onto pins).
The work from this commit makes that possible during scans of nbtree
unlogged indexes -- without our having to give up on setting LP_DEAD
bits on index tuples altogether.

Follow-up to commit d774072f, which moved the fake LSN infrastructure
out of GiST so that it could be used by other index AMs.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Andres Freund <andres@anarazel.de>
Reviewed-By: Tomas Vondra <tomas@vondra.me>
Discussion: https://postgr.es/m/CAH2-WzkehuhxyuA8quc7rRN3EtNXpiKsjPfO8mhb+0Dr2K0Dtg@mail.gmail.com
2026-03-13 20:37:39 -04:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Change copyObject() to use typeof_unqual 2026-03-13 07:06:57 +01:00
contrib Initialize variable to placate compiler. 2026-03-13 11:32:14 -05:00
doc Add stats_reset column to pg_stat_database_conflicts. 2026-03-13 22:17:14 +09:00
src Use fake LSNs to improve nbtree dropPin behavior. 2026-03-13 20:37:39 -04:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:34 -04:00
.cirrus.tasks.yml Revert "Change default value of default_toast_compression to "lz4"" 2026-03-05 08:25:35 +09:00
.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 b6eb8dde6b to .git-blame-ignore-revs. 2026-03-13 11:45:34 -05:00
.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 Change copyObject() to use typeof_unqual 2026-03-13 07:06:57 +01:00
configure.ac Change copyObject() to use typeof_unqual 2026-03-13 07:06:57 +01:00
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 Restore AIX support. 2026-02-23 13:34:22 -05:00
meson.build Change copyObject() to use typeof_unqual 2026-03-13 07:06:57 +01:00
meson_options.txt Update copyright for 2026 2026-01-01 13:24:10 -05:00
README.md Revise the style of a paragraph in README.md. 2024-03-21 10:16:41 -05:00

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/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/.