Fixed #7298: prevent update() on sliced QuerySet since UPDATE doesn't reliably support LIMIT/OFFSET. Thanks, George Vilches.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7601 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/modeltests/update/models.py

@@ -63,5 +63,12 @@ a manager method.
 >>> DataPoint.objects.values('value').distinct()
 [{'value': u'thing'}]
 
+We do not support update on already sliced query sets.
+
+>>> DataPoint.objects.all()[:2].update(another_value='another thing')
+Traceback (most recent call last):
+    ...
+AssertionError: Cannot update a query once a slice has been taken.
+
 """
 }