diff options
| author | Manuel Weitzman <manuelweitzman@gmail.com> | 2020-05-10 12:25:06 -0400 |
|---|---|---|
| committer | Mariusz Felisiak <felisiak.mariusz@gmail.com> | 2020-05-21 10:51:10 +0200 |
| commit | a4e6030904df63b3f10aa0729b86dc6942b0458e (patch) | |
| tree | 7a84def5f8bd0e0376a471fa238f74f429e25478 /docs/ref/models/querysets.txt | |
| parent | 0e893248b28e30bf562d29e6d5745ffad4b1a1eb (diff) | |
Fixed #30375 -- Added FOR NO KEY UPDATE support to QuerySet.select_for_update() on PostgreSQL.
Diffstat (limited to 'docs/ref/models/querysets.txt')
| -rw-r--r-- | docs/ref/models/querysets.txt | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt index b96cd67e98..2e862dbbb7 100644 --- a/docs/ref/models/querysets.txt +++ b/docs/ref/models/querysets.txt @@ -1663,7 +1663,7 @@ For example:: ``select_for_update()`` ~~~~~~~~~~~~~~~~~~~~~~~ -.. method:: select_for_update(nowait=False, skip_locked=False, of=()) +.. method:: select_for_update(nowait=False, skip_locked=False, of=(), no_key=False) Returns a queryset that will lock rows until the end of the transaction, generating a ``SELECT ... FOR UPDATE`` SQL statement on supported databases. @@ -1708,6 +1708,12 @@ to refer to the queryset's model. Restaurant.objects.select_for_update(of=('self', 'place_ptr')) +On PostgreSQL only, you can pass ``no_key=True`` in order to acquire a weaker +lock, that still allows creating rows that merely reference locked rows +(through a foreign key, for example) whilst the lock is in place. The +PostgreSQL documentation has more details about `row-level lock modes +<https://www.postgresql.org/docs/current/explicit-locking.html#LOCKING-ROWS>`_. + You can't use ``select_for_update()`` on nullable relations:: >>> Person.objects.select_related('hometown').select_for_update() @@ -1725,8 +1731,9 @@ Currently, the ``postgresql``, ``oracle``, and ``mysql`` database backends support ``select_for_update()``. However, MariaDB 10.3+ supports only the ``nowait`` argument and MySQL 8.0.1+ supports the ``nowait`` and ``skip_locked`` arguments. MySQL and MariaDB don't support the ``of`` argument. +The ``no_key`` argument is supported only on PostgreSQL. -Passing ``nowait=True``, ``skip_locked=True``, or ``of`` to +Passing ``nowait=True``, ``skip_locked=True``, ``no_key=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. @@ -1758,6 +1765,10 @@ raised if ``select_for_update()`` is used in autocommit mode. PostgreSQL doesn't support ``select_for_update()`` with :class:`~django.db.models.expressions.Window` expressions. +.. versionchanged:: 3.2 + + The ``no_key`` argument was added. + ``raw()`` ~~~~~~~~~ |