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David Rowley 5d56d07ca3 Optimize tuplestore usage for WITH RECURSIVE CTEs 
nodeRecursiveunion.c makes use of two tuplestores and, until now, would
delete and recreate one of these tuplestores after every recursive
iteration.

Here we adjust that behavior and instead reuse one of the existing
tuplestores and just empty it of all tuples using tuplestore_clear().

This saves some free/malloc roundtrips and has shown a 25-30% performance
improvement for queries that perform very little work between recursive
iterations.

This also paves the way to add some EXPLAIN ANALYZE telemetry output for
recursive common table expressions, similar to what was done in 1eff8279d
and 95d6e9af0.  Previously calling tuplestore_end() would have caused
the maximum storage space used to be lost.

Reviewed-by: Tatsuo Ishii
Discussion: https://postgr.es/m/CAApHDvr9yW0YRiK8A2J7nvyT8g17YzbSfOviEWrghazKZbHbig@mail.gmail.com
2024-09-19 15:20:35 +12:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config jit: Remove {llvm-config,clang}-N configure probes. 2024-05-16 13:58:25 +12:00
contrib postgres_fdw: Extend postgres_fdw_get_connections to return user name. 2024-09-18 12:51:48 +09:00
doc doc PG relnotes: add paragraph explaining the section symbol 2024-09-18 17:13:19 -04:00
src Optimize tuplestore usage for WITH RECURSIVE CTEs 2024-09-19 15:20:35 +12:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml Add PG_TEST_PG_COMBINEBACKUP_MODE to CI tasks 2024-09-10 16:30:38 +02:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add commit 7229ebe011 to .git-blame-ignore-revs. 2024-09-14 20:17:30 +02:00
.gitattributes Remove non-existing file from .gitattributes 2024-02-16 11:39:09 +01:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Remove support for OpenSSL older than 1.1.0 2024-09-02 13:51:48 +02:00
configure.ac Remove support for OpenSSL older than 1.1.0 2024-09-02 13:51:48 +02:00
COPYRIGHT Update copyright for 2024 2024-01-03 20:49:05 -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 Improve meson's detection of perl build flags 2024-09-14 10:26:25 -04:00
meson_options.txt Remove spinlocks and atomics from meson_options.txt. 2024-07-30 23:37:14 +12:00
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/.