diff options
| -rw-r--r-- | rest_framework/relations.py | 64 | ||||
| -rw-r--r-- | tests/test_relations_hyperlink.py | 12 |
2 files changed, 45 insertions, 31 deletions
diff --git a/rest_framework/relations.py b/rest_framework/relations.py index 75d68204..ae4086ec 100644 --- a/rest_framework/relations.py +++ b/rest_framework/relations.py @@ -84,9 +84,34 @@ class RelatedField(Field): queryset = queryset.all() return queryset + def use_pk_only_optimization(self): + return False + + def get_attribute(self, instance): + if self.use_pk_only_optimization(): + try: + # Optimized case, return a mock object only containing the pk attribute. + instance = get_attribute(instance, self.source_attrs[:-1]) + return PKOnlyObject(pk=instance.serializable_value(self.source_attrs[-1])) + except AttributeError: + pass + + # Standard case, return the object instance. + return get_attribute(instance, self.source_attrs) + def get_iterable(self, instance, source_attrs): relationship = get_attribute(instance, source_attrs) - return relationship.all() if (hasattr(relationship, 'all')) else relationship + relationship = relationship.all() if (hasattr(relationship, 'all')) else relationship + + if self.use_pk_only_optimization(): + # Optimized case, return mock objects only containing the pk attribute. + return [ + PKOnlyObject(pk=pk) + for pk in relationship.values_list('pk', flat=True) + ] + + # Standard case, return the object instances. + return relationship @property def choices(self): @@ -120,6 +145,9 @@ class PrimaryKeyRelatedField(RelatedField): 'incorrect_type': _('Incorrect type. Expected pk value, received {data_type}.'), } + def use_pk_only_optimization(self): + return True + def to_internal_value(self, data): try: return self.get_queryset().get(pk=data) @@ -128,32 +156,6 @@ class PrimaryKeyRelatedField(RelatedField): except (TypeError, ValueError): self.fail('incorrect_type', data_type=type(data).__name__) - def get_attribute(self, instance): - # We customize `get_attribute` here for performance reasons. - # For relationships the instance will already have the pk of - # the related object. We return this directly instead of returning the - # object itself, which would require a database lookup. - try: - instance = get_attribute(instance, self.source_attrs[:-1]) - return PKOnlyObject(pk=instance.serializable_value(self.source_attrs[-1])) - except AttributeError: - return get_attribute(instance, self.source_attrs) - - def get_iterable(self, instance, source_attrs): - # For consistency with `get_attribute` we're using `serializable_value()` - # here. Typically there won't be any difference, but some custom field - # types might return a non-primitive value for the pk otherwise. - # - # We could try to get smart with `values_list('pk', flat=True)`, which - # would be better in some case, but would actually end up with *more* - # queries if the developer is using `prefetch_related` across the - # relationship. - relationship = super(PrimaryKeyRelatedField, self).get_iterable(instance, source_attrs) - return [ - PKOnlyObject(pk=item.serializable_value('pk')) - for item in relationship - ] - def to_representation(self, value): return value.pk @@ -184,6 +186,9 @@ class HyperlinkedRelatedField(RelatedField): super(HyperlinkedRelatedField, self).__init__(**kwargs) + def use_pk_only_optimization(self): + return self.lookup_field == 'pk' + def get_object(self, view_name, view_args, view_kwargs): """ Return the object corresponding to a matched URL. @@ -285,6 +290,11 @@ class HyperlinkedIdentityField(HyperlinkedRelatedField): kwargs['source'] = '*' super(HyperlinkedIdentityField, self).__init__(view_name, **kwargs) + def use_pk_only_optimization(self): + # We have the complete object instance already. We don't need + # to run the 'only get the pk for this relationship' code. + return False + class SlugRelatedField(RelatedField): """ diff --git a/tests/test_relations_hyperlink.py b/tests/test_relations_hyperlink.py index b938e385..e741e99b 100644 --- a/tests/test_relations_hyperlink.py +++ b/tests/test_relations_hyperlink.py @@ -89,7 +89,8 @@ class HyperlinkedManyToManyTests(TestCase): {'url': 'http://testserver/manytomanysource/2/', 'name': 'source-2', 'targets': ['http://testserver/manytomanytarget/1/', 'http://testserver/manytomanytarget/2/']}, {'url': 'http://testserver/manytomanysource/3/', 'name': 'source-3', 'targets': ['http://testserver/manytomanytarget/1/', 'http://testserver/manytomanytarget/2/', 'http://testserver/manytomanytarget/3/']} ] - self.assertEqual(serializer.data, expected) + with self.assertNumQueries(4): + self.assertEqual(serializer.data, expected) def test_reverse_many_to_many_retrieve(self): queryset = ManyToManyTarget.objects.all() @@ -99,7 +100,8 @@ class HyperlinkedManyToManyTests(TestCase): {'url': 'http://testserver/manytomanytarget/2/', 'name': 'target-2', 'sources': ['http://testserver/manytomanysource/2/', 'http://testserver/manytomanysource/3/']}, {'url': 'http://testserver/manytomanytarget/3/', 'name': 'target-3', 'sources': ['http://testserver/manytomanysource/3/']} ] - self.assertEqual(serializer.data, expected) + with self.assertNumQueries(4): + self.assertEqual(serializer.data, expected) def test_many_to_many_update(self): data = {'url': 'http://testserver/manytomanysource/1/', 'name': 'source-1', 'targets': ['http://testserver/manytomanytarget/1/', 'http://testserver/manytomanytarget/2/', 'http://testserver/manytomanytarget/3/']} @@ -197,7 +199,8 @@ class HyperlinkedForeignKeyTests(TestCase): {'url': 'http://testserver/foreignkeysource/2/', 'name': 'source-2', 'target': 'http://testserver/foreignkeytarget/1/'}, {'url': 'http://testserver/foreignkeysource/3/', 'name': 'source-3', 'target': 'http://testserver/foreignkeytarget/1/'} ] - self.assertEqual(serializer.data, expected) + with self.assertNumQueries(1): + self.assertEqual(serializer.data, expected) def test_reverse_foreign_key_retrieve(self): queryset = ForeignKeyTarget.objects.all() @@ -206,7 +209,8 @@ class HyperlinkedForeignKeyTests(TestCase): {'url': 'http://testserver/foreignkeytarget/1/', 'name': 'target-1', 'sources': ['http://testserver/foreignkeysource/1/', 'http://testserver/foreignkeysource/2/', 'http://testserver/foreignkeysource/3/']}, {'url': 'http://testserver/foreignkeytarget/2/', 'name': 'target-2', 'sources': []}, ] - self.assertEqual(serializer.data, expected) + with self.assertNumQueries(3): + self.assertEqual(serializer.data, expected) def test_foreign_key_update(self): data = {'url': 'http://testserver/foreignkeysource/1/', 'name': 'source-1', 'target': 'http://testserver/foreignkeytarget/2/'} |