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 b7b0f3f27241 introduces a code path bypassing this check. Author: Jim Jones <[email protected]> Author: Daniil Davydov <[email protected]> Co-authored-by: Alexander Korotkov <[email protected]> Reviewed-by: Michael Paquier <[email protected]> Reviewed-by: Soumya S Murali <[email protected]> Reviewed-by: Tom Lane <[email protected]> Discussion: https://postgr.es/m/CAJDiXghdFcZ8%3Dnh4G69te7iRr3Q0uFyXxb3ZdG09_GTNZXwH0g%40mail.gmail.com Backpatch-through: 17 Branch ------ REL_17_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/40927d458fe1a8c96bcf418b47169f0f6eb15946 Modified Files -------------- src/include/utils/rel.h | 14 ++ src/test/modules/test_misc/meson.build | 1 + .../test_misc/t/013_temp_obj_multisession.pl | 260 +++++++++++++++++++++ 3 files changed, 275 insertions(+)
