0ec3f048bf
The RI fast-path FK check asserted that the referenced key is never NULL, in ri_FastPathFlushArray() and in recheck_matched_pk_tuple(). That holds for a primary key, but a foreign key may reference any unique column, and a UNIQUE column is nullable. The assertion is reachable under READ COMMITTED. ri_LockPKTuple() locks the matched PK tuple with TUPLE_LOCK_FLAG_FIND_LAST_VERSION, so when a concurrent transaction commits a key-changing UPDATE while the check waits, the lock follows the update chain to the latest version. If that version now has NULL in the referenced column, the fast path reaches the assert; in a non-assert build it would compare against the NULL and treat it as a match. A NULL referenced key cannot equal any (non-null) FK value, so treat it as no match and let the ordinary foreign-key violation be raised. This matches the SPI path, whose requalifying "pkatt = $n" evaluates to NULL for such a row, so the row is not returned and the check reports a violation. Reported-by: Noah Misch <noah@leadboat.com> Reviewed-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com> Discussion: https://postgr.es/m/20260705210533.ee.noahmisch@microsoft.com Backpatch-through: 19
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/.