implement BaseQuerySet.batch_size

tests/queryset/queryset.py

@@ -337,6 +337,36 @@ class QuerySetTest(unittest.TestCase):
         query = query.filter(boolfield=True)
         self.assertEqual(query.count(), 1)
 
+    def test_batch_size(self):
+        """Ensure that batch_size works."""
+        class A(Document):
+            s = StringField()
+
+        A.drop_collection()
+
+        for i in range(100):
+            A.objects.create(s=str(i))
+
+        # test iterating over the result set
+        cnt = 0
+        for a in A.objects.batch_size(10):
+            cnt += 1
+        self.assertEqual(cnt, 100)
+
+        # test chaining
+        qs = A.objects.all()
+        qs = qs.limit(10).batch_size(20).skip(91)
+        cnt = 0
+        for a in qs:
+            cnt += 1
+        self.assertEqual(cnt, 9)
+
+        # test invalid batch size
+        qs = A.objects.batch_size(-1)
+        self.assertRaises(ValueError, lambda: list(qs))
+        qs = A.objects.filter(s='1').batch_size('not a number')
+        self.assertRaises(TypeError, lambda: [doc for doc in qs])
+
     def test_update_write_concern(self):
         """Test that passing write_concern works"""
         self.Person.drop_collection()