Group queries for SlugRelatedField many serializers

Author: clement-escolano

rest_framework/relations.py

@@ -4,7 +4,7 @@
 from urllib import parse
 
 from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist
-from django.db.models import Manager
+from django.db.models import F, Manager
 from django.db.models.query import QuerySet
 from django.urls import NoReverseMatch, Resolver404, get_script_prefix, resolve
 from django.utils.encoding import smart_str, uri_to_iri
@@ -458,15 +458,26 @@ def __init__(self, slug_field=None, **kwargs):
         self.slug_field = slug_field
         super().__init__(**kwargs)
 
-    def to_internal_value(self, data):
+    def to_many_internal_value(self, data):
         queryset = self.get_queryset()
         try:
-            return queryset.get(**{self.slug_field: data})
-        except ObjectDoesNotExist:
-            self.fail('does_not_exist', slug_name=self.slug_field, value=smart_str(data))
+            result = (
+                queryset
+                .filter(**{self.slug_field + "__in": data})
+                .annotate(_slug_field_value=F(self.slug_field))
+                .all()
+            )
+            slugs = [item._slug_field_value for item in result]
+            for item in data:
+                if item not in slugs:
+                    self.fail('does_not_exist', slug_name=self.slug_field, value=smart_str(item))
+            return result
         except (TypeError, ValueError):
             self.fail('invalid')
 
+    def to_internal_value(self, data):
+        return self.to_many_internal_value([data])[0]
+
     def to_representation(self, obj):
         slug = self.slug_field
         if "__" in slug:

tests/test_relations_slug.py

@@ -174,6 +174,12 @@ def test_reverse_foreign_key_create(self):
         ]
         assert serializer.data == expected
 
+    def test_reverse_foreign_key_create_grouped_queries(self):
+        data = {'id': 3, 'name': 'target-3', 'sources': ['source-1', 'source-3']}
+        serializer = ForeignKeyTargetSerializer(data=data)
+        with self.assertNumQueries(1):
+            assert serializer.is_valid()
+
     def test_foreign_key_update_with_invalid_null(self):
         data = {'id': 1, 'name': 'source-1', 'target': None}
         instance = ForeignKeySource.objects.get(pk=1)

tests/utils.py

@@ -35,7 +35,7 @@ def all(self):
         return list(self.items)
 
     def filter(self, **lookup):
-        return MockQueryset(
+        return MockQueryset([
             item
             for item in self.items
             if all([
@@ -44,7 +44,13 @@ def filter(self, **lookup):
                 else attrgetter(key.replace('__', '.'))(item) == value
                 for key, value in lookup.items()
             ])
-        )
+        ])
+
+    def annotate(self, **kwargs):
+        for key, value in kwargs.items():
+            for item in self.items:
+                setattr(item, key, attrgetter(value.name.replace('__', '.'))(item))
+        return self
 
 
 class BadType: