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Richard Guo cc5d98525d Fix incorrect handling of subquery pullup
When pulling up a subquery, if the subquery's target list items are
used in grouping set columns, we need to wrap them in PlaceHolderVars.
This ensures that expressions retain their separate identity so that
they will match grouping set columns when appropriate.

In 90947674f, we decided to wrap subquery outputs that are non-var
expressions in PlaceHolderVars.  This prevents const-simplification
from merging them into the surrounding expressions after subquery
pullup, which could otherwise lead to failing to match those
subexpressions to grouping set columns, with the effect that they'd
not go to null when expected.

However, that left some loose ends.  If the subquery's target list
contains two or more identical Var expressions, we can still fail to
match the Var expression to the expected grouping set expression.
This is not related to const-simplification, but rather to how we
match expressions to lower target items in setrefs.c.

For sort/group expressions, we use ressortgroupref matching, which
works well.  For other expressions, we primarily rely on comparing the
expressions to determine if they are the same.  Therefore, we need a
way to prevent setrefs.c from matching the expression to some other
identical ones.

To fix, wrap all subquery outputs in PlaceHolderVars if the parent
query uses grouping sets, ensuring that they preserve their separate
identity throughout the whole planning process.

Reported-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/CAMbWs4-meSahaanKskpBn0KKxdHAXC1_EJCVWHxEodqirrGJnw@mail.gmail.com
2025-03-13 16:36:03 +09:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
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contrib Fix indentation issue 2025-03-13 12:41:44 +13:00
doc pg_rewind: Add dbname to primary_conninfo when using --write-recovery-conf. 2025-03-12 16:56:04 -07:00
src Fix incorrect handling of subquery pullup 2025-03-13 16:36:03 +09:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
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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/.