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Tom Lane ce571434ae Remove race condition in pg_get_expr().
Since its introduction, pg_get_expr() has intended to silently
return NULL if called with an invalid relation OID, as can happen
when scanning the catalogs concurrently with relation drops.
However, there is a race condition: we check validity of the OID
at the start, but it could get dropped just afterward, leading to
failures.  This is the cause of some intermittent instability we're
seeing in a proposed new test case, and presumably it's a hazard in
the field as well.

We can fix this by AccessShareLock-ing the target relation for the
duration of pg_get_expr().  Since we don't require any permissions
on the target relation, this is semantically a bit undesirable.  But
it turns out that the set_relation_column_names() subroutine already
takes a transient AccessShareLock on that relation, and has done since
commit 2ffa740be in 2012.  Given the lack of complaints about that, it
seems like there should be no harm in holding the lock a bit longer.

Back-patch to all supported branches.

Discussion: https://postgr.es/m/31ddcc01-a71b-4e8c-9948-01d1c47293ca@eisentraut.org
2024-02-09 12:29:41 -05:00
config jit: Require at least LLVM 10. 2024-01-25 15:42:34 +13:00
contrib pgcrypto: Fix check for buffer size 2024-01-30 11:15:46 +01:00
doc doc: Remove superfluous bracket in synopsis 2024-02-08 12:19:34 +01:00
src Remove race condition in pg_get_expr(). 2024-02-09 12:29:41 -05:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml ci: Enable injection points in builds 2024-01-23 12:01:18 +09:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
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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/.