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Fixed #22491 -- documented how `select_for_update() should be tested. #2982

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Fixed #22491 -- documented how `select_for_update() should be tested. #2982

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18 changes: 15 additions & 3 deletions docs/ref/models/querysets.txt
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Expand Up @@ -1421,9 +1421,10 @@ do not support ``nowait``, such as MySQL, will cause a
unexpectedly blocking.

Evaluating a queryset with ``select_for_update`` in autocommit mode is
an error because the rows are then not locked. If allowed, this would
facilitate data corruption, and could easily be caused by calling,
outside of any transaction, code that expects to be run in one.
a :exc:`~django.db.transaction.TransactionManagementError` error because the
rows are then not locked. If allowed, this would facilitate data corruption, and
could easily be caused by calling, outside of any transaction, code that expects
to be run in one.

Using ``select_for_update`` on backends which do not support
``SELECT ... FOR UPDATE`` (such as SQLite) will have no effect.
Expand All @@ -1433,6 +1434,17 @@ Using ``select_for_update`` on backends which do not support
It is now an error to execute a query with ``select_for_update()`` in
autocommit mode. With earlier releases in the 1.6 series it was a no-op.

.. warning::

Although `select_for_update() normally fails in autocommit mode, since
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please use 4 space indent
missing after select_for_update() on this line (but actually all instances of single should be `` for proper formatting)

:class:`~django.test.TestCase` automatically wraps each test in a transaction,
calling `select_for_update()` in a `TestCase` even without an
:func:`~django.db.transaction.atomic()` block will unexpectedly
pass without raising a `TransactionManagementError`. To properly test
`select_for_update()` you should use
:class:`~django.test.TransactionTestCase`.

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1 newline between sections


raw
~~~

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5 changes: 4 additions & 1 deletion docs/topics/testing/tools.txt
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Expand Up @@ -636,7 +636,10 @@ to test the effects of commit and rollback:
While ``commit`` and ``rollback`` operations still *appear* to work when
used in ``TestCase``, no actual commit or rollback will be performed by the
database. This can cause your tests to pass or fail unexpectedly. Always
use ``TransactionTestCase`` when testing transactional behavior.
use ``TransactionTestCase`` when testing transactional behavior or any code
that can't normally be excuted in autocommit mode
(:meth:`~django.db.models.query.QuerySet.select_for_update()` is an
example).

``TransactionTestCase`` inherits from :class:`~django.test.SimpleTestCase`.

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