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David Rowley 7027dd499d Remove deduplication logic from find_window_functions 
This code thought it was optimizing WindowAgg evaluation by getting rid
of duplicate WindowFuncs, but it turns out all it does today is lead to
cost-underestimations and makes it possible that optimize_window_clauses
could miss some of the WindowFuncs that must receive an updated winref.

The deduplication likely was useful when it was first added, but since
the projection code was changed in b8d7f053c, the list of WindowFuncs
gathered by find_window_functions isn't used during execution.  Instead,
the expression evaluation code will process the node's targetlist to find
the WindowFuncs.

The reason the deduplication could cause issues for
optimize_window_clauses() is because if a WindowFunc is moved to another
WindowClause, the winref is adjusted to reference the new WindowClause.
If any duplicate WindowFuncs were discarded in find_window_functions()
then the WindowFuncLists may not include all the WindowFuncs that need
their winref adjusted.  This could lead to an error message such as:

ERROR:  WindowFunc with winref 2 assigned to WindowAgg with winref 1

The back-branches will receive a different fix so that the WindowAgg costs
are not affected.

Author: Meng Zhang <mza117jc@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAErYLFAuxmW0UVdgrz7iiuNrxGQnFK_OP9hBD5CUzRgjrVrz=Q@mail.gmail.com
2026-01-26 23:27:15 +13:00
.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 pg_stat_statements: Fix test instability with cache-clobbering builds 2026-01-25 19:01:23 +09:00
doc Add pg_restore_extended_stats() 2026-01-26 15:08:15 +09:00
src Remove deduplication logic from find_window_functions 2026-01-26 23:27:15 +13:00
.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/.