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Richard Guo 1132af22cf Fix HAVING-to-WHERE pushdown for simple-CASE form
Commit f76686ce7 added a walker that detects when a HAVING clause uses
a collation that conflicts with the GROUP BY's nondeterministic
collation, keeping such clauses in HAVING.  The walker uses
exprInputCollation() to identify each ancestor's comparison collation,
but missed the simple-CASE case: parse analysis builds each WHEN as
OpExpr(CaseTestExpr op val), where CaseTestExpr is a placeholder for
the arg, while the actual arg expression sits at cexpr->arg, outside
the OpExpr that carries the comparison's inputcollid.  A GROUP Var at
cexpr->arg was therefore visited with the WHEN's inputcollid absent
from the ancestor stack, the conflict went undetected, and the clause
was wrongly pushed to WHERE.

Fix by handling simple CASE explicitly: before walking cexpr->arg,
push every WHEN's inputcollid onto the ancestor stack so a GROUP Var
at the arg is checked against the same collations the WHEN comparisons
would apply.  Then walk the WHEN bodies and defresult under the
unchanged stack, where their own collation contexts are picked up by
the default path.

Back-patch to v18 only; this fix extends the walker added by commit
f76686ce7 and inherits its dependency on the v18 RTE_GROUP mechanism.

Author: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Reviewed-by: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/CAHg+QDcqPdd=2V0PQ_oNYj50OUeqSqznqFaYtP3RdokLBDXBqw@mail.gmail.com
Backpatch-through: 18
2026-05-08 10:59:13 +09:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Allow PG_PRINTF_ATTRIBUTE to be different in C and C++ code. 2026-02-25 11:57:26 -05:00
contrib postgres_fdw: Fix handling of abort-cleanup-failed connections. 2026-05-05 18:55:02 +09:00
doc doc: Mention validation attempt during ALTER INDEX .. ATTACH PARTITION 2026-05-01 13:10:38 +09:00
src Fix HAVING-to-WHERE pushdown for simple-CASE form 2026-05-08 10:59:13 +09:00
.abi-compliance-history Update .abi-compliance-history for AddRelationNotNullConstraints(). 2026-02-21 13:08:44 +01:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:53 -04:00
.cirrus.tasks.yml Fix typo 2026-01-07 15:48:45 +01:00
.cirrus.yml ci: Per-repo configuration for manually trigger tasks 2025-08-14 11:33:44 -04:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add script to keep .editorconfig in sync with .gitattributes 2025-02-01 10:09:45 +01:00
.git-blame-ignore-revs Add previous commit to .git-blame-ignore-revs. 2025-10-21 10:02:19 -05:00
.gitattributes Fix git whitespace warning 2025-08-15 10:32:22 +02:00
.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 Allow PG_PRINTF_ATTRIBUTE to be different in C and C++ code. 2026-02-25 11:57:26 -05:00
configure.ac Allow PG_PRINTF_ATTRIBUTE to be different in C and C++ code. 2026-02-25 11:57:26 -05:00
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 Adapt REL_18_STABLE to its new status as a stable branch 2025-06-29 23:00:00 -04:00
meson.build Allow PG_PRINTF_ATTRIBUTE to be different in C and C++ code. 2026-02-25 11:57:26 -05:00
meson_options.txt Add support for basic NUMA awareness 2025-04-07 23:08:17 +02:00
README.md Adapt REL_18_STABLE to its new status as a stable branch 2025-06-29 23:00:00 -04:00

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/18/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/18/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/.