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Refs #34840 -- Improved release note describing index regression.

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Adam Johnson 2023-10-15 09:27:11 +01:00 committed by GitHub
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docs/releases/4.2.6.txt
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@ -35,9 +35,16 @@ Bugfixes
* Fixed a regression in Django 4.2 that caused unnecessary casting of string
based fields (``CharField``, ``EmailField``, ``TextField``, ``CICharField``,
``CIEmailField``, and ``CITextField``) used with the ``__isnull`` lookup on
PostgreSQL. As a consequence, the pre-Django 4.2 indexes didn't match and
were not used by the query planner (:ticket:`34840`).
PostgreSQL. As a consequence, indexes using an ``__isnull`` expression or
condition created before Django 4.2 wouldn't be used by the query planner,
leading to a performance regression (:ticket:`34840`).
You may need to recreate indexes propagated to the database with Django
4.2 - 4.2.5 as they contain unnecessary ``::text`` casting that is avoided as
of this release.
You may need to recreate such indexes created in your database with Django
4.2 to 4.2.5, as they contain unnecessary ``::text`` casting. Find candidate
indexes with this query:
.. code-block:: sql
SELECT indexname, indexdef
FROM pg_indexes
WHERE indexdef LIKE '%::text IS %NULL';