Peter Geoghegan e6eed40e44 Avoid BufferGetLSNAtomic() calls during nbtree scans. Delay calling BufferGetLSNAtomic() until we finish reading a page that actually contains items that btgettuple will return to the executor. This reduces the number of calls during plain index scans (we'll only call BufferGetLSNAtomic() when _bt_readpage returns true), and totally eliminates calls during index-only scans, bitmap index scans, and plain index scans of an unlogged relation. Currently, when checksums (or wal_log_hints) are enabled, acquiring a page's LSN in BufferGetLSNAtomic() involves locking the buffer header (which involves the use of spinlocks). Testing has shown that enabling page-level checksums causes large regressions with certain workloads, especially on larger multi-socket systems. The regression isn't tied to any Postgres 18 commit. However, Postgres 18 commit `04bec894` made initdb use checksums by default, so it seems prudent to address the problem now. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Tomas Vondra <tomas@vondra.me> Discussion: https://postgr.es/m/941f0190-e3c6-4622-9ac7-c04e936e5fdb@vondra.me Discussion: https://postgr.es/m/CAH2-Wzk-Dg5XWs_jDuiHt4_7ryrSY+n=vxmHY51EVqPDFsKXmg@mail.gmail.com		6 months ago
.github	Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md.	1 year ago
config	oauth: Move the builtin flow into a separate module	8 months ago
contrib	pg_prewarm: Allow autoprewarm to use more than 1GB to dump blocks.	6 months ago
doc	Doc: improve description of which role runs a trigger.	7 months ago
src	Avoid BufferGetLSNAtomic() calls during nbtree scans.	6 months ago
.cirrus.star	Remove duplicate words in docs and code comments.	2 years ago
.cirrus.tasks.yml	ci: Check for missing dependencies in meson builds	8 months ago
.cirrus.yml	ci: Test NetBSD and OpenBSD	10 months ago
.dir-locals.el	Make Emacs perl-mode indent more like perltidy.	7 years ago
.editorconfig	Add script to keep .editorconfig in sync with .gitattributes	11 months ago
.git-blame-ignore-revs	Add commit `4672b6223` to .git-blame-ignore-revs.	7 months ago
.gitattributes	Add script to keep .editorconfig in sync with .gitattributes	11 months ago
.gitignore	Update top-level .gitignore.	3 years ago
.mailmap	Add a Git .mailmap file	1 year ago
COPYRIGHT	Align organization wording in copyright statement	7 months ago
GNUmakefile.in	Allow selecting the git revision to be packaged by "make dist".	2 years ago
HISTORY	Canonicalize some URLs	6 years ago
Makefile	Remove AIX support	2 years ago
README.md	Revise the style of a paragraph in README.md.	2 years ago
aclocal.m4	autoconf: Move export_dynamic determination to configure	3 years ago
configure	Make our usage of memset_s() conform strictly to the C11 standard.	7 months ago
configure.ac	Make our usage of memset_s() conform strictly to the C11 standard.	7 months ago
meson.build	Make our usage of memset_s() conform strictly to the C11 standard.	7 months ago
meson_options.txt	Add support for basic NUMA awareness	8 months ago

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.

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/.