Added tests for many to one batch fetching

sqlalchemy_utils/functions/batch_fetch.py

@@ -189,15 +189,11 @@ class CompoundFetcher(AbstractFetcher):
             *[fetcher.condition for fetcher in self.fetchers]
         )
 
-    def fetcher_for_entity(self, entity):
-        for fetcher in self.fetchers:
-            if getattr(entity, fetcher.remote_column_name) is not None:
-                return fetcher
-
     def fetch(self):
-        self.parent_dict = defaultdict(list)
         for entity in self.related_entities:
-            self.fetcher_for_entity(entity).append_entity(entity)
+            for fetcher in self.fetchers:
+                if getattr(entity, fetcher.remote_column_name) is not None:
+                    fetcher.append_entity(entity)
 
     def populate(self):
         for fetcher in self.fetchers:

tests/batch_fetch/test_compound_fetching.py

@@ -107,3 +107,105 @@ class TestCompoundOneToManyBatchFetching(TestCase):
         assert self.business_premises[2].equipment
         assert self.business_premises[2].equipment[0].name == 'E 4'
         assert self.connection.query_count == query_count
+
+
+class TestCompoundManyToOneBatchFetching(TestCase):
+    def create_models(self):
+        class Equipment(self.Base):
+            __tablename__ = 'equipment'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.Unicode(255))
+
+        class Building(self.Base):
+            __tablename__ = 'building'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.Unicode(255))
+
+            equipment_id = sa.Column(sa.Integer, sa.ForeignKey(Equipment.id))
+
+            equipment = sa.orm.relationship(Equipment)
+
+        class BusinessPremise(self.Base):
+            __tablename__ = 'business_premise'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.Unicode(255))
+
+            building_id = sa.Column(sa.Integer, sa.ForeignKey(Building.id))
+
+            building = sa.orm.relationship(
+                Building,
+                backref=sa.orm.backref(
+                    'business_premises'
+                )
+            )
+
+            equipment_id = sa.Column(sa.Integer, sa.ForeignKey(Equipment.id))
+
+            equipment = sa.orm.relationship(Equipment)
+
+        self.Building = Building
+        self.BusinessPremise = BusinessPremise
+        self.Equipment = Equipment
+
+    def setup_method(self, method):
+        TestCase.setup_method(self, method)
+        self.equipment = [
+            self.Equipment(
+                id=2, name=u'E 1',
+            ),
+            self.Equipment(
+                id=4, name=u'E 2',
+            ),
+            self.Equipment(
+                id=6, name=u'E 3',
+            ),
+            self.Equipment(
+                id=8, name=u'E 4',
+            ),
+        ]
+        self.buildings = [
+            self.Building(id=12, name=u'B 1', equipment=self.equipment[0]),
+            self.Building(id=15, name=u'B 2', equipment=self.equipment[1]),
+            self.Building(id=19, name=u'B 3'),
+        ]
+        self.business_premises = [
+            self.BusinessPremise(
+                id=22,
+                name=u'BP 1',
+                building=self.buildings[0]
+            ),
+            self.BusinessPremise(
+                id=33,
+                name=u'BP 2',
+                building=self.buildings[0],
+                equipment=self.equipment[2]
+            ),
+            self.BusinessPremise(
+                id=44,
+                name=u'BP 3',
+                building=self.buildings[2],
+                equipment=self.equipment[1]
+            ),
+        ]
+
+        self.session.add_all(self.buildings)
+        self.session.add_all(self.business_premises)
+        self.session.add_all(self.equipment)
+        self.session.commit()
+
+    def test_compound_fetching(self):
+        buildings = self.session.query(self.Building).all()
+        batch_fetch(
+            buildings,
+            'business_premises',
+            compound_path(
+                'equipment',
+                'business_premises.equipment'
+            )
+        )
+        query_count = self.connection.query_count
+
+        assert buildings[0].equipment.name == 'E 1'
+        assert buildings[1].equipment.name == 'E 2'
+        assert buildings[2].business_premises[0].equipment.name == 'E 2'
+        assert self.connection.query_count == query_count