[1.4.x] Fixed SQLite's collapsing of same-valued instances in bulk_create

SQLite used INSERT INTO tbl SELECT %s UNION SELECT %s, the problem
was that there should have been UNION ALL instead of UNION.

Refs #19351

Backpatch of a27582484cf814554907d2d1ad077852de36963f

2 files changed, 9 insertions, 1 deletions

diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index 2146a7fa8a..f31d2ab3eb 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -215,7 +215,7 @@ class DatabaseOperations(BaseDatabaseOperations):
         res.append("SELECT %s" % ", ".join(
             "%%s AS %s" % self.quote_name(f.column) for f in fields
         ))
-        res.extend(["UNION SELECT %s" % ", ".join(["%s"] * len(fields))] * (num_values - 1))
+        res.extend(["UNION ALL SELECT %s" % ", ".join(["%s"] * len(fields))] * (num_values - 1))
         return " ".join(res)
 
 class DatabaseWrapper(BaseDatabaseWrapper):
diff --git a/tests/regressiontests/bulk_create/tests.py b/tests/regressiontests/bulk_create/tests.py
index b4c3e7f17f..f75d983a06 100644
--- a/tests/regressiontests/bulk_create/tests.py
+++ b/tests/regressiontests/bulk_create/tests.py
@@ -59,6 +59,14 @@ class BulkCreateTests(TestCase):
             "CA", "IL", "ME", "NY",
         ], attrgetter("two_letter_code"))
 
+    def test_batch_same_vals(self):
+        # Sqlite had a problem where all the same-valued models were
+        # collapsed to one insert.
+        Restaurant.objects.bulk_create([
+            Restaurant(name='foo') for i in range(0, 2)
+        ])
+        self.assertEqual(Restaurant.objects.count(), 2)
+
     def test_large_batch(self):
         with override_settings(DEBUG=True):
             connection.queries = []