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Melanie Plageman 648a7e28d7 Eliminate use of cached VM value in lazy_scan_prune() 
lazy_scan_prune() takes a parameter from lazy_scan_heap() indicating
whether the page was marked all-visible in the VM at the time it was
last checked in find_next_unskippable_block(). This behavior is
historical, dating back to commit 608195a3a3, when we did not pin the
VM page until deciding we must read it. Now that the VM page is already
pinned, there is no meaningful benefit to relying on a cached VM status.

Removing this cached value simplifies the logic in both lazy_scan_heap()
and lazy_scan_prune(). It also clarifies future work that will set the
visibility map on-access: such paths will not have a cached value
available, which would make the logic harder to reason about. And
eliminating it enables us to detect and repair VM corruption on-access.

Along with removing the cached value and unconditionally checking the
visibility status of the heap page, this commit also moves the VM
corruption handling to occur first. This reordering should have no
performance impact, since the checks are inexpensive and performed only
once per page. It does, however, make the control flow easier to
understand. The new restructuring also makes it possible to set the VM
after fixing corruption (if pruning found the page all-visible).

Now that no callers of visibilitymap_set() use its return value, change
its (and visibilitymap_set_vmbits()) return type to void.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Discussion: https://postgr.es/m/5CEAA162-67B1-44DA-B60D-8B65717E8B05%40gmail.com
2026-01-26 17:00:13 -05:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Update copyright for 2026 2026-01-01 13:24:10 -05:00
contrib Combine visibilitymap_set() cases in lazy_scan_prune() 2026-01-26 16:03:32 -05:00
doc doc: Clarify that \d and \d+ output lists are illustrative, not exhaustive. 2026-01-26 20:45:05 +09:00
src Eliminate use of cached VM value in lazy_scan_prune() 2026-01-26 17:00:13 -05:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:34 -04:00
.cirrus.tasks.yml ci: Configure g++ with 32-bit for 32-bit build 2026-01-09 08:58:50 +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 Detect if flags are needed for C++11 support 2026-01-22 09:09:25 +01:00
configure.ac Detect if flags are needed for C++11 support 2026-01-22 09:09:25 +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 Remove AIX support 2024-02-28 15:17:23 +04:00
meson.build Detect if flags are needed for C++11 support 2026-01-22 09:09:25 +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/.