Alexander Korotkov
1cd37a7a8d
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
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.
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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.
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