From 03049fb8d96ccd1f1ed0285486103542de42faba Mon Sep 17 00:00:00 2001 From: Ran Benita Date: Tue, 17 Oct 2017 11:28:00 +0800 Subject: Refs #28010 -- Allowed reverse related fields in SELECT FOR UPDATE .. OF. Thanks Adam Chidlow for polishing the patch. --- docs/ref/models/querysets.txt | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'docs') diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt index fe2c827e63..bd20fbdcea 100644 --- a/docs/ref/models/querysets.txt +++ b/docs/ref/models/querysets.txt @@ -1628,6 +1628,19 @@ 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. +You can't use ``select_for_update()`` on nullable relations:: + + >>> Person.objects.select_related('hometown').select_for_update() + Traceback (most recent call last): + ... + django.db.utils.NotSupportedError: FOR UPDATE cannot be applied to the nullable side of an outer join + +To avoid that restriction, you can exclude null objects if you don't care about +them:: + + >>> Person.objects.select_related('hometown').select_for_update().exclude(hometown=None) + , ...]> + Currently, the ``postgresql``, ``oracle``, and ``mysql`` database backends support ``select_for_update()``. However, MySQL doesn't support the ``nowait``, ``skip_locked``, and ``of`` arguments. -- cgit v1.3