Ticket #18556: 18556.diff

django/db/models/fields/related.py

@@ -542 +542 @@
             if rel_field.null:
                 def remove(self, *objs):
                     val = getattr(self.instance, attname)
+                    ids = []
                     for obj in objs:
                         # Is obj actually part of this descriptor set?
                         if getattr(obj, rel_field.attname) == val:
-                            setattr(obj, rel_field.name, None)
-                            obj.save()
+                            ids.append(obj.pk)
                         else:
                             raise rel_field.rel.to.DoesNotExist("%r is not related to %r." % (obj, self.instance))
+                    self.filter(pk__in=ids).update(**{rel_field.name: None})
                 remove.alters_data = True
 
                 def clear(self):

docs/ref/models/relations.txt

@@ -91 +91 @@
         :class:`~django.db.models.ForeignKey` doesn't have ``null=True``, this
         is invalid.
 
+        .. versionchanged:: 1.6
+
+        The ``remove()`` method executes one query regardless of the number of
+        objects being removed. In prior versions, it executed one query per
+        object by calling the ``save()`` method of each object being removed.
+
     .. method:: clear()
 
         Removes all objects from the related object set::

docs/releases/1.6.txt

@@ -108 +108 @@
     deprecation timeline for a given feature, its removal may appear as a
     backwards incompatible change.
 
+*  The :meth:`~django.db.models.fields.related.RelatedManager.remove` method on
+   a reverse foreign key now does one query regardless of the number of objects
+   removed rather than one query per object. The ``save()`` method of the
+   objects being removed is no longer called and thus
+   :data:`~django.db.models.signals.pre_save` and
+   :data:`~django.db.models.signals.post_save` signals are no longer sent. This
+   is consistent with how
+   :meth:`~django.db.models.fields.related.RelatedManager.clear` works.
+
 Features deprecated in 1.6
 ==========================
 

tests/modeltests/many_to_one_null/tests.py

@@ -93 +93 @@
         with self.assertNumQueries(1):
             r.article_set.clear()
         self.assertEqual(r.article_set.count(), 0)
+
+    def test_remove_efficiency(self):
+        r = Reporter.objects.create()
+        articles = []
+        for _ in xrange(3):
+            articles.append(r.article_set.create())
+        with self.assertNumQueries(1):
+            r.article_set.remove(*articles)
+        self.assertEqual(r.article_set.count(), 0)