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Tom Lane e83a8ae447 Don't use a tuplestore if we don't have to for SQL-language functions.
We only need a tuplestore if we're actually going to accumulate
multiple result tuples.  Obviously then we don't need one for non-set-
returning functions; but even a SRF doesn't need one if we decide to
use "lazyEval" (one row at a time) mode.  In these cases, it's
sufficient to use the junkfilter's result slot to hold the single row
that's due to be returned.  We just need to "materialize" that slot
to ensure it holds onto the data past shutdown of the sub-executor.

The original intent of this patch was partially to save a few cycles
(by not putting tuples into a tuplestore only to pull them back out
immediately), but mostly to ensure that we don't use a tuplestore
in non-set-returning functions.  That's because I had concerns
about whether a tuplestore is safe to keep across queries,
which was possible for functions invoked via long-lived FmgrInfos
such as those kept in the typcache.  There are no cases where SRFs
are called that way, so getting rid of the tuplestore in non-SRFs
should make things safer.

However, it emerges that running fmgr_sql in a short-lived context
(as 595d1efed made it do) makes the existing coding unsafe anyway:
we can end up with a long-lived TupleTableSlot holding a freeable
reference to a short-lived tuple, resulting in a double-free crash.
Not trying to pull tuples out of the tuplestore using that slot
dodges the problem, so I'm going to commit this now rather than
invent a band-aid solution for v18.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/2443532.1744919968@sss.pgh.pa.us
Discussion: https://postgr.es/m/9f975803-1a1c-4f21-b987-f572e110e860@gmail.com
2025-05-02 16:16:20 -04:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config oauth: Move the builtin flow into a separate module 2025-05-01 09:14:30 -07:00
contrib oauth: Disallow OAuth connections via postgres_fdw/dblink 2025-04-29 13:08:24 -07:00
doc Doc: correct spelling of meson switch. 2025-05-02 15:12:49 -04:00
src Don't use a tuplestore if we don't have to for SQL-language functions. 2025-05-02 16:16:20 -04:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml ci: Check for missing dependencies in meson builds 2025-04-09 22:01:58 +02:00
.cirrus.yml ci: Test NetBSD and OpenBSD 2025-02-12 09:40:07 -05:00
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GNUmakefile.in Allow selecting the git revision to be packaged by "make dist". 2024-05-03 11:08:50 -04:00
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Makefile Remove AIX support 2024-02-28 15:17:23 +04:00
meson_options.txt Add support for basic NUMA awareness 2025-04-07 23:08:17 +02:00
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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/.