E.2. Release 17.9
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## E.2. Release 17.9 #

Release date: 2026-02-26

This release contains a small number of fixes from 17.8. For information about new features in major release 17, see Section E.11.

### E.2.1. Migration to Version 17.9 #

A dump/restore is not required for those running 17.X.

However, if you are upgrading from a version earlier than 17.6, see Section E.5.

### E.2.2. 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 computation of the set of potentially-nulling outer joins for the output of a `LATERAL UNION ALL` subquery (Richard Guo) §

  This error could lead to skipping `NOT NULL` tests in the mistaken belief that they were unnecessary, resulting in wrong query output.

- 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.

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