diff options
Diffstat (limited to 'docs/ref/models')
| -rw-r--r-- | docs/ref/models/querysets.txt | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt index a9006a14a9..d8d063a7a5 100644 --- a/docs/ref/models/querysets.txt +++ b/docs/ref/models/querysets.txt @@ -1611,7 +1611,7 @@ For example:: ``select_for_update()`` ~~~~~~~~~~~~~~~~~~~~~~~ -.. method:: select_for_update(nowait=False, skip_locked=False) +.. method:: select_for_update(nowait=False, skip_locked=False, of=()) Returns a queryset that will lock rows until the end of the transaction, generating a ``SELECT ... FOR UPDATE`` SQL statement on supported databases. @@ -1635,14 +1635,21 @@ queryset is evaluated. You can also ignore locked rows by using ``select_for_update()`` with both options enabled will result in a :exc:`ValueError`. +By default, ``select_for_update()`` locks all rows that are selected by the +query. For example, rows of related objects specified in :meth:`select_related` +are locked in addition to rows of the queryset's model. If this isn't desired, +specify the related objects you want to lock in ``select_for_update(of=(...))`` +using the same fields syntax as :meth:`select_related`. Use the value ``'self'`` +to refer to the queryset's model. + Currently, the ``postgresql``, ``oracle``, and ``mysql`` database backends support ``select_for_update()``. However, MySQL doesn't support the -``nowait`` and ``skip_locked`` arguments. +``nowait``, ``skip_locked``, and ``of`` arguments. -Passing ``nowait=True`` or ``skip_locked=True`` to ``select_for_update()`` -using database backends that do not support these options, such as MySQL, -raises a :exc:`~django.db.NotSupportedError`. This prevents code from -unexpectedly blocking. +Passing ``nowait=True``, ``skip_locked=True``, or ``of`` to +``select_for_update()`` using database backends that do not support these +options, such as MySQL, raises a :exc:`~django.db.NotSupportedError`. This +prevents code from unexpectedly blocking. Evaluating a queryset with ``select_for_update()`` in autocommit mode on backends which support ``SELECT ... FOR UPDATE`` is a @@ -1670,6 +1677,10 @@ raised if ``select_for_update()`` is used in autocommit mode. The ``skip_locked`` argument was added. +.. versionchanged:: 2.0 + + The ``of`` argument was added. + ``raw()`` ~~~~~~~~~ |