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Alexander Korotkov 1fee0e857e Add tests for cross-session temp table access
Add a TAP test in src/test/modules/test_misc that documents what
happens when one session attempts to read or modify another session's
temporary table.  This commit only adds tests; it does not change
backend behavior, so the assertions reflect current behavior:

- SELECT, UPDATE, DELETE, MERGE, COPY on a table without an index
  silently succeed with no error and zero rows / zero affected rows.
  These commands run through the read-stream path, which currently
  bypasses the RELATION_IS_OTHER_TEMP() check.  This is the
  underlying bug to be fixed in a follow-up.
- INSERT errors with "cannot access temporary tables of other
  sessions" because hio.c calls ReadBufferExtended() to find a page
  with free space and is caught by the existing check there.
- Index scan errors via the same existing check, reached through
  nbtree -> ReadBuffer -> ReadBufferExtended.
- TRUNCATE / ALTER TABLE / ALTER INDEX / CLUSTER fail with their
  command-specific error messages.
- VACUUM is silently skipped to avoid noise during database-wide
  VACUUM (vacuum_rel() returns without warning).
- DROP TABLE is intentionally allowed: DROP does not touch the
  table's contents, and autovacuum relies on this to clean up
  temp relations orphaned by a crashed backend.
- ALTER FUNCTION / DROP FUNCTION on an owner-created function over
  its own temp row type work as catalog operations -- they don't
  read the underlying data.
- CREATE FUNCTION from a separate session, using another session's
  temp row type as an argument, is allowed but emits a NOTICE: the
  function is moved into the creator's pg_temp namespace with an
  auto-dependency on the borrowed type, so it disappears together
  with the session that created it.
- A bare DROP TABLE on a temp table that has a cross-session
  dependent function fails with a catalog-level dependency error.
- LOCK TABLE in ACCESS SHARE mode on another session's temp table
  succeeds and properly blocks the owner's session-exit cleanup
  (which acquires AccessExclusiveLock via findDependentObjects).
  This exercises the same LockRelationOid path used by autovacuum
  when cleaning up orphaned temp relations.
- When the owner session ends, the normal session-exit cleanup
  cascades through DEPENDENCY_NORMAL and removes both the temp
  objects and any cross-session functions that depended on them.

Also, document the contract for RELATION_IS_OTHER_TEMP() so that
future buffer-access entry points enforce the same rule.

Backpatch this through PostgreSQL 17, where b7b0f3f272 introduces a code
path bypassing this check.

Author: Jim Jones <jim.jones@uni-muenster.de>
Author: Daniil Davydov <3danissimo@gmail.com>
Co-authored-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Soumya S Murali <soumyamurali.work@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAJDiXghdFcZ8%3Dnh4G69te7iRr3Q0uFyXxb3ZdG09_GTNZXwH0g%40mail.gmail.com
Backpatch-through: 17
2026-05-14 15:01:17 +03:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Update config.guess and config.sub 2026-04-09 11:26:14 +02:00
contrib postgres_fdw: Fix deparsing of remote column names in stats import. 2026-05-14 17:05:00 +09:00
doc Use "grep -E" not "egrep". 2026-05-13 12:07:19 -04:00
src Add tests for cross-session temp table access 2026-05-14 15:01:17 +03:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:34 -04:00
.cirrus.tasks.yml Enable test_cplusplusext with MSVC 2026-04-01 07:48:47 +02:00
.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 several commits to .git-blame-ignore-revs. 2026-05-13 14:53:48 -05:00
.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 Add errdetail() with PID and UID about source of termination signal. 2026-04-07 10:22:33 -04:00
configure.ac Add errdetail() with PID and UID about source of termination signal. 2026-04-07 10:22:33 -04:00
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 Restore AIX support. 2026-02-23 13:34:22 -05:00
meson.build Meson: Fix check_header() for readline and gssapi 2026-04-20 12:36:14 +09:00
meson_options.txt Revert "Add built-in fuzzing harnesses for security testing." 2026-04-10 09:53:58 -04:00
README.md Revise the style of a paragraph in README.md. 2024-03-21 10:16:41 -05:00

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/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/.