Masahiko Sawada eef9cc4dc2 Reduce memory block size for decoded tuple storage to 8kB. Commit `a4ccc1cef` introduced the Generation Context and modified the logical decoding process to use a Generation Context with a fixed block size of 8MB for storing tuple data decoded during logical decoding (i.e., rb->tup_context). Several reports have indicated that the logical decoding process can be terminated due to out-of-memory (OOM) situations caused by excessive memory usage in rb->tup_context. This issue can occur when decoding a workload involving several concurrent transactions, including a long-running transaction that modifies tuples. By design, the Generation Context does not free a memory block until all chunks within that block are released. Consequently, if tuples modified by the long-running transaction are stored across multiple memory blocks, these blocks remain allocated until the long-running transaction completes, leading to substantial memory fragmentation. The memory usage during logical decoding, tracked by rb->size, does not account for memory fragmentation, resulting in potentially much higher memory consumption than the value of the logical_decoding_work_mem parameter. Various improvement strategies were discussed in the relevant thread. This change reduces the block size of the Generation Context used in rb->tup_context from 8MB to 8kB. This modification significantly decreases the likelihood of substantial memory fragmentation occurring and is relatively straightforward to backport. Performance testing across multiple platforms has confirmed that this change will not introduce any performance degradation that would impact actual operation. Backport to all supported branches. Reported-by: Alex Richman, Michael Guissine, Avi Weinberg Reviewed-by: Amit Kapila, Fujii Masao, David Rowley Tested-by: Hayato Kuroda, Shlok Kyal Discussion: https://postgr.es/m/CAD21AoBTY1LATZUmvSXEssvq07qDZufV4AF-OHh9VD2pC0VY2A%40mail.gmail.com Backpatch-through: 12		1 year ago
config	jit: Remove {llvm-config,clang}-N configure probes.	2 years ago
contrib	Stabilize the test added by commit `022564f60c`.	1 year ago
doc	doc PG 17 relnotes: clarify pg_upgrade and logical slot preserv.	1 year ago
src	Reduce memory block size for decoded tuple storage to 8kB.	1 year ago
.cirrus.star	Remove duplicate words in docs and code comments.	2 years ago
.cirrus.tasks.yml	ci: Pin MacPorts version to 2.9.3.	1 year ago
.cirrus.yml	ci: Make compute resources for CI configurable	2 years ago
.dir-locals.el	…
.editorconfig	…
.git-blame-ignore-revs	Add commit `7229ebe011` to .git-blame-ignore-revs.	1 year ago
.gitattributes	Remove non-existing file from .gitattributes	2 years ago
.gitignore	Update top-level .gitignore.	3 years ago
COPYRIGHT	Update copyright for 2024	2 years ago
GNUmakefile.in	Allow selecting the git revision to be packaged by "make dist".	2 years ago
HISTORY	…
Makefile	Adapt REL_17_STABLE to its new status as a stable branch	2 years ago
README.md	Adapt REL_17_STABLE to its new status as a stable branch	2 years ago
aclocal.m4	autoconf: Move export_dynamic determination to configure	3 years ago
configure	Stamp 17.0.	1 year ago
configure.ac	Stamp 17.0.	1 year ago
meson.build	Stamp 17.0.	1 year ago
meson_options.txt	Allow selecting the git revision to be packaged by "make dist".	2 years 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/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/.