PostgreSQL 15.17 release changes

Fix failure after replaying a multixid truncation record from WAL that was generated by an older minor version (Heikki Linnakangas) §

Erroneous logic for coping with the way that previous versions handled multixid wraparound led to replay failure, with messages like “could not access status of transaction”. A typical scenario in which this could occur is a standby server of the latest minor version consuming WAL from a primary server of an older version.

Avoid incorrect complaint of invalid encoding when substring() is applied to “toasted” data (Noah Misch) § § §

The fix for CVE-2026-2006 was too aggressive and could raise an error about an incomplete character in cases that are actually valid.

Fix pg_stat_get_backend_wait_event() and pg_stat_get_backend_wait_event_type() to report values for auxiliary processes (Heikki Linnakangas) §

Previously these functions returned NULL for auxiliary processes, but that's inconsistent with the pg_stat_activity view.

Fix casting a composite-type variable to a domain type when returning its value from a PL/pgSQL function (Tom Lane) §

If the variable's value is NULL, a “cache lookup failed for type 0” error resulted.

Fix potential null pointer dereference in contrib/hstore's binary input function (Michael Paquier) §

hstore's receive function crashed on input containing duplicate keys. hstore values generated by Postgres would never contain duplicate keys, so this mistake has gone unnoticed. The crash could be provoked by malicious or corrupted data.