Fixed #17602 -- Stopped the XML serializer from doing unneeded queries. Thanks, gnosek.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17439 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/serializers/python.py

@@ -45,18 +45,12 @@ class Serializer(base.Serializer):
             self._current[field.name] = field.value_to_string(obj)
 
     def handle_fk_field(self, obj, field):
-        related = getattr(obj, field.name)
-        if related is not None:
-            if self.use_natural_keys and hasattr(related, 'natural_key'):
-                related = related.natural_key()
-            else:
-                if field.rel.field_name == related._meta.pk.name:
-                    # Related to remote object via primary key
-                    related = related._get_pk_val()
-                else:
-                    # Related to remote object via other field
-                    related = smart_unicode(getattr(related, field.rel.field_name), strings_only=True)
-        self._current[field.name] = related
+        if self.use_natural_keys and hasattr(field.rel.to, 'natural_key'):
+            related = getattr(obj, field.name)
+            value = related.natural_key()
+        else:
+            value = getattr(obj, field.get_attname())
+        self._current[field.name] = value
 
     def handle_m2m_field(self, obj, field):
         if field.rel.through._meta.auto_created:

django/core/serializers/xml_serializer.py

@@ -85,9 +85,10 @@ class Serializer(base.Serializer):
         differently from regular fields).
         """
         self._start_relational_field(field)
-        related = getattr(obj, field.name)
-        if related is not None:
-            if self.use_natural_keys and hasattr(related, 'natural_key'):
+        related_att = getattr(obj, field.get_attname())
+        if related_att is not None:
+            if self.use_natural_keys and hasattr(field.rel.to, 'natural_key'):
+                related = getattr(obj, field.name)
                 # If related object has a natural key, use it
                 related = related.natural_key()
                 # Iterable natural keys are rolled out as subelements
@@ -96,13 +97,7 @@ class Serializer(base.Serializer):
                     self.xml.characters(smart_unicode(key_value))
                     self.xml.endElement("natural")
             else:
-                if field.rel.field_name == related._meta.pk.name:
-                    # Related to remote object via primary key
-                    related = related._get_pk_val()
-                else:
-                    # Related to remote object via other field
-                    related = getattr(related, field.rel.field_name)
-                self.xml.characters(smart_unicode(related))
+                self.xml.characters(smart_unicode(related_att))
         else:
             self.xml.addQuickElement("None")
         self.xml.endElement("field")

tests/modeltests/serializers/tests.py

@@ -178,6 +178,19 @@ class SerializersTestBase(object):
         mv_obj = obj_list[0].object
         self.assertEqual(mv_obj.title, movie_title)
 
+    def test_serialize_superfluous_queries(self):
+        """Ensure no superfluous queries are made when serializing ForeignKeys
+
+        #17602
+        """
+        ac = Actor(name='Actor name')
+        ac.save()
+        mv = Movie(title='Movie title', actor_id=ac.pk)
+        mv.save()
+
+        with self.assertNumQueries(0):
+            serial_str = serializers.serialize(self.serializer_name, [mv])
+
     def test_serialize_with_null_pk(self):
         """
         Tests that serialized data with no primary key results