Expand tests, ensure foreign keys are not dereferenced

django/db/models/query.py

@@ -486,20 +486,31 @@ def bulk_save(self, objs, fields, batch_size=None):
             raise ValueError('All objects must have a primary key set')
         if not objs:
             return
-        fields = list(fields)
+        fields = [self.model._meta.get_field(name) for name in list(fields)]
+        if any(not f.concrete for f in fields):
+            raise ValueError('bulk_save can only be used with concrete fields')
+
+        field_names = [f.attname for f in fields]
+
         ops = connections[self.db].ops
         # We use PK twice in the resulting update query, once in the filter
         # and once in the WHEN.
-        batch_size = (batch_size or max(ops.bulk_batch_size(['pk', 'pk'] + fields, objs), 1))
+        max_batch_size = ops.bulk_batch_size(['pk', 'pk'] + fields, objs)
+        if not batch_size:
+            batch_size = max_batch_size
+        else:
+            batch_size = min(batch_size, max_batch_size)
+
+        batches = (objs[i:i + batch_size] for i in range(0, len(objs), batch_size))
         with transaction.atomic(using=self.db, savepoint=False):
-            for batch_objs in [objs[i:i + batch_size] for i in range(0, len(objs), batch_size)]:
+            for batch_objs in batches:
                 pks = [obj.pk for obj in batch_objs]
                 update_kwargs = {
-                    field: Case(
-                        *(When(pk=obj.pk, then=Value(getattr(obj, field)))
+                    name: Case(
+                        *(When(pk=obj.pk, then=Value(getattr(obj, name)))
                           for obj in batch_objs)
                     )
-                    for field in fields
+                    for name in field_names
                 }
                 self.filter(pk__in=pks).update(**update_kwargs)
     bulk_save.alters_data = True

tests/bulk_save/models.py

@@ -8,7 +8,8 @@ class Town(models.Model):
 class Place(models.Model):
     name = models.CharField(max_length=255)
     rating = models.IntegerField()
-    town = models.ForeignKey(Town, related_name='places', on_delete=models.CASCADE, null=True)
+    town = models.ForeignKey(Town, related_name='places', on_delete=models.SET_NULL, null=True)
+    db_custom_column = models.IntegerField(db_column='custom_column_name', default=0)
 
     if connection.vendor == 'postgresql':
         from django.contrib.postgres.fields import ArrayField, JSONField

tests/bulk_save/test_bulk_save.py

@@ -3,11 +3,13 @@
 from django.db import connection
 from django.test import TestCase
 
-from .models import Place, Pub
+from .models import Place, Pub, Town
 
 
 class BulkSaveTests(TestCase):
     def setUp(self):
+        self.town = Town.objects.create(name='Saffron Walden')
+
         self.pubs = [
             Pub.objects.create(name='The Temeraire', rating=-10, ambiance=-10),
             Pub.objects.create(name='The Rose and Crown', rating=5, ambiance=7),
@@ -77,6 +79,21 @@ def test_no_models_no_queries(self):
         with self.assertNumQueries(0):
             Pub.objects.bulk_save([], fields=['name'])
 
+    def test_only_concrete_fields_allowed(self):
+        msg = "bulk_save can only be used with concrete fields"
+        with self.assertRaisesMessage(ValueError, msg):
+            Town.objects.bulk_save([self.town], fields=['places'])
+
+    def test_custom_db_columns(self):
+        Place.objects.bulk_save(self.places, fields=['db_custom_column'])
+
+    def test_foreign_keys_do_not_lookup(self):
+        for place in self.places:
+            place.town = self.town
+
+        with self.assertNumQueries(1):
+            Place.objects.bulk_save(self.places, ['town'])
+
 
 @unittest.skipUnless(connection.vendor == 'postgres', 'Postgres tests')
 class PostgresComplexFieldsTest(TestCase):
@@ -97,5 +114,3 @@ def test_array_of_json(self):
         place.array_of_json = [{'a': 'b'}, {'c': 'd'}]
         Place.objects.bulk_save([place], fields=['array_of_json'])
         self.assertDictEqual(Place.objects.get().array_of_json, [{'a': 'b'}, {'c': 'd'}])
-
-# connection.features.gis_enabled