[1.10.x] Fixed #27385 -- Fixed QuerySet.bulk_create() on PostgreSQL when the number of objects is a multiple plus one of batch_size.

Backport of b3bd3aa07c026239dd39d1a37498dfd0a2f09caf from master

3 files changed, 16 insertions, 6 deletions

diff --git a/django/db/models/query.py b/django/db/models/query.py
index dd2a6001d0..42943a7f28 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -1060,9 +1060,9 @@ class QuerySet(object):
         for item in [objs[i:i + batch_size] for i in range(0, len(objs), batch_size)]:
             if connections[self.db].features.can_return_ids_from_bulk_insert:
                 inserted_id = self._insert(item, fields=fields, using=self.db, return_id=True)
-                if len(objs) > 1:
+                if isinstance(inserted_id, list):
                     inserted_ids.extend(inserted_id)
-                if len(objs) == 1:
+                else:
                     inserted_ids.append(inserted_id)
             else:
                 self._insert(item, fields=fields, using=self.db)
diff --git a/docs/releases/1.10.3.txt b/docs/releases/1.10.3.txt
index a45124fb3a..5bb340a3a8 100644
--- a/docs/releases/1.10.3.txt
+++ b/docs/releases/1.10.3.txt
@@ -20,3 +20,6 @@ Bugfixes
 
 * Made the ``JavaScriptCatalog`` view respect the ``packages`` argument;
   previously it was ignored (:ticket:`27374`).
+
+* Fixed ``QuerySet.bulk_create()`` on PostgreSQL when the number of objects is
+  a multiple plus one of ``batch_size`` (:ticket:`27385`).
diff --git a/tests/bulk_create/tests.py b/tests/bulk_create/tests.py
index e6d85cb815..3378f0010a 100644
--- a/tests/bulk_create/tests.py
+++ b/tests/bulk_create/tests.py
@@ -171,11 +171,18 @@ class BulkCreateTests(TestCase):
 
     def test_explicit_batch_size(self):
         objs = [TwoFields(f1=i, f2=i) for i in range(0, 4)]
-        TwoFields.objects.bulk_create(objs, 2)
-        self.assertEqual(TwoFields.objects.count(), len(objs))
+        num_objs = len(objs)
+        TwoFields.objects.bulk_create(objs, batch_size=1)
+        self.assertEqual(TwoFields.objects.count(), num_objs)
         TwoFields.objects.all().delete()
-        TwoFields.objects.bulk_create(objs, len(objs))
-        self.assertEqual(TwoFields.objects.count(), len(objs))
+        TwoFields.objects.bulk_create(objs, batch_size=2)
+        self.assertEqual(TwoFields.objects.count(), num_objs)
+        TwoFields.objects.all().delete()
+        TwoFields.objects.bulk_create(objs, batch_size=3)
+        self.assertEqual(TwoFields.objects.count(), num_objs)
+        TwoFields.objects.all().delete()
+        TwoFields.objects.bulk_create(objs, batch_size=num_objs)
+        self.assertEqual(TwoFields.objects.count(), num_objs)
 
     def test_empty_model(self):
         NoFields.objects.bulk_create([NoFields() for i in range(2)])