Documented that the update() method on querysets is a direct SQL call, not the

same as looping over the queryset and calling save() on each item (which is
less efficient). Fixed #7447.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7884 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/db-api.txt

@@ -2212,6 +2212,18 @@ updated is that it can only access one database table, the model's main
 table. So don't try to filter based on related fields or anything like that;
 it won't work.
 
+Be aware that the ``update()`` method is converted directly to an SQL
+statement. It is a bulk operation for direct updates. It doesn't run any
+``save()`` methods on your models, or emit the ``pre_save`` or ``post_save``
+signals (which are a consequence of calling ``save()``). If you want to save
+every item in a ``QuerySet`` and make sure that the ``save()`` method is
+called on each instance, you don't need any special function to handle that.
+Just loop over them and call ``save()``:
+
+    for item in my_queryset:
+        item.save()
+
+
 Extra instance methods
 ======================