non_polymorphic() queryset member function added

polymorphic/query.py

@@ -42,6 +42,13 @@ class PolymorphicQuerySet(QuerySet):
         new.polymorphic_disabled = self.polymorphic_disabled
         return new
 
+    def non_polymorphic(self, *args, **kwargs):
+        """switch off polymorphic behaviour for this query.
+        When the queryset is evaluated, only objects of the type of the
+        base class used for this query are returned."""
+        self.polymorphic_disabled = True
+        return self
+
     def instance_of(self, *args):
         """Filter the queryset to only include the classes in args (and their subclasses).
         Implementation in _translate_polymorphic_filter_defnition."""

polymorphic/tests.py

@@ -289,6 +289,13 @@ __test__ = {"doctest": """
 >>> o.get_real_instance()
 <Model2C: id 3, field1 (CharField), field2 (CharField), field3 (CharField)>
 
+# non_polymorphic()
+>>> Model2A.objects.all().non_polymorphic()
+[ <Model2A: id 1, field1 (CharField)>,
+  <Model2A: id 2, field1 (CharField)>,
+  <Model2A: id 3, field1 (CharField)>,
+  <Model2A: id 4, field1 (CharField)> ]
+
 
 ### test inheritance pointers & _base_managers