Group queries for PrimaryKeyRelatedField many serializers

rest_framework/relations.py

@@ -249,18 +249,25 @@ class PrimaryKeyRelatedField(RelatedField):
     def use_pk_only_optimization(self):
         return True
 
-    def to_internal_value(self, data):
+    def to_many_internal_value(self, data):
         if self.pk_field is not None:
-            data = self.pk_field.to_internal_value(data)
+            data = [self.pk_field.to_internal_value(item) for item in data]
         queryset = self.get_queryset()
         try:
-            if isinstance(data, bool):
-                raise TypeError
-            return queryset.get(pk=data)
-        except ObjectDoesNotExist:
-            self.fail('does_not_exist', pk_value=data)
+            for item in data:
+                if isinstance(item, bool):
+                    raise TypeError
+            result = queryset.filter(pk__in=data).all()
+            pks = [item.pk for item in result]
+            for item in data:
+                if item not in pks:
+                    self.fail('does_not_exist', pk_value=item)
+            return result
         except (TypeError, ValueError):
-            self.fail('incorrect_type', data_type=type(data).__name__)
+            self.fail('incorrect_type', data_type=type(data[0]).__name__)
+
+    def to_internal_value(self, data):
+        return self.to_many_internal_value([data])[0]
 
     def to_representation(self, value):
         if self.pk_field is not None:
@@ -524,6 +531,9 @@ class ManyRelatedField(Field):
         if not self.allow_empty and len(data) == 0:
             self.fail('empty')
 
+        if hasattr(self.child_relation, "to_many_internal_value"):
+            return self.child_relation.to_many_internal_value(data)
+
         return [
             self.child_relation.to_internal_value(item)
             for item in data

tests/test_relations_pk.py

@@ -189,6 +189,13 @@ class PKManyToManyTests(TestCase):
         ]
         assert serializer.data == expected
 
+    def test_many_to_many_grouped_queries(self):
+        data = {'id': 4, 'name': 'source-4', 'targets': [1, 3]}
+        serializer = ManyToManySourceSerializer(data=data)
+        # Only one query should be executed even with several targets
+        with self.assertNumQueries(1):
+            assert serializer.is_valid()
+
     def test_many_to_many_unsaved(self):
         source = ManyToManySource(name='source-unsaved')
 

tests/utils.py

@@ -26,14 +26,26 @@ class MockQueryset:
         return self.items[val]
 
     def get(self, **lookup):
-        for item in self.items:
-            if all([
-                attrgetter(key.replace('__', '.'))(item) == value
-                for key, value in lookup.items()
-            ]):
-                return item
+        result = self.filter(**lookup).all()
+        if len(result) > 0:
+            return result[0]
         raise ObjectDoesNotExist()
 
+    def all(self):
+        return list(self.items)
+
+    def filter(self, **lookup):
+        return MockQueryset(
+            item
+            for item in self.items
+            if all([
+                attrgetter(key.replace("__in", "").replace('__', '.'))(item) in value
+                if key.endswith("__in")
+                else attrgetter(key.replace('__', '.'))(item) == value
+                for key, value in lookup.items()
+            ])
+        )
+
 
 class BadType:
     """