Merge pull request #510 from mldwg/related_accessor

Caching in inheritance accessor functions

Author: bckohan

src/polymorphic/models.py

@@ -201,11 +201,15 @@ def __init__(self, *args, **kwargs):
             return
         self.__class__.polymorphic_super_sub_accessors_replaced = True
 
-        def create_accessor_function_for_model(model, accessor_name):
+        def create_accessor_function_for_model(model, field):
             def accessor_function(self):
-                objects = getattr(model, "_base_objects", model.objects)
-                attr = objects.get(pk=self.pk)
-                return attr
+                try:
+                    rel_obj = field.get_cached_value(self)
+                except KeyError:
+                    objects = getattr(model, "_base_objects", model.objects)
+                    rel_obj = objects.get(pk=self.pk)
+                    field.set_cached_value(self, rel_obj)
+                return rel_obj
 
             return accessor_function
 
@@ -218,10 +222,16 @@ def accessor_function(self):
                 type(orig_accessor),
                 (ReverseOneToOneDescriptor, ForwardManyToOneDescriptor),
             ):
+                field = (
+                    orig_accessor.related
+                    if isinstance(orig_accessor, ReverseOneToOneDescriptor)
+                    else orig_accessor.field
+                )
+
                 setattr(
                     self.__class__,
                     name,
-                    property(create_accessor_function_for_model(model, name)),
+                    property(create_accessor_function_for_model(model, field)),
                 )
 
     def _get_inheritance_relation_fields_and_models(self):

src/polymorphic/tests/test_orm.py

@@ -973,6 +973,29 @@ def test_parent_link_and_related_name(self):
         # test that we can delete the object
         t.delete()
 
+    def test_polymorphic__accessor_caching(self):
+        blog_a = BlogA.objects.create(name="blog")
+
+        blog_base = BlogBase.objects.non_polymorphic().get(id=blog_a.id)
+        blog_a = BlogA.objects.get(id=blog_a.id)
+
+        # test reverse accessor & check that we get back cached object on repeated access
+        self.assertEqual(blog_base.bloga, blog_a)
+        self.assertIs(blog_base.bloga, blog_base.bloga)
+        cached_blog_a = blog_base.bloga
+
+        # test forward accessor & check that we get back cached object on repeated access
+        self.assertEqual(blog_a.blogbase_ptr, blog_base)
+        self.assertIs(blog_a.blogbase_ptr, blog_a.blogbase_ptr)
+        cached_blog_base = blog_a.blogbase_ptr
+
+        # check that refresh_from_db correctly clears cached related objects
+        blog_base.refresh_from_db()
+        blog_a.refresh_from_db()
+
+        self.assertIsNot(cached_blog_a, blog_base.bloga)
+        self.assertIsNot(cached_blog_base, blog_a.blogbase_ptr)
+
     def test_polymorphic__aggregate(self):
         """test ModelX___field syntax on aggregate (should work for annotate either)"""