Fixed #27507 -- Used SchemaEditor.execute() to run deferred_sql in migrate's sync_apps().

django/core/management/commands/migrate.py

@@ -312,8 +312,9 @@ class Command(BaseCommand):
 
                 if self.verbosity >= 1:
                     self.stdout.write("    Running deferred SQL...\n")
+                with connection.schema_editor() as editor:
                     for statement in deferred_sql:
-                    cursor.execute(statement)
+                        editor.execute(statement)
         finally:
             cursor.close()
 

tests/migrations/migrations_test_apps/unmigrated_app_syncdb/models.py

@@ -0,0 +1,9 @@
+from django.db import models
+
+
+class Classroom(models.Model):
+    pass
+
+
+class Lesson(models.Model):
+    classroom = models.ForeignKey(Classroom, on_delete=models.CASCADE)

tests/migrations/test_commands.py

@@ -12,6 +12,7 @@ from django.core.management import CommandError, call_command
 from django.db import (
     ConnectionHandler, DatabaseError, connection, connections, models,
 )
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.migrations.exceptions import (
     InconsistentMigrationHistory, MigrationSchemaMissing,
 )
@@ -461,6 +462,20 @@ class MigrateTests(MigrationTestBase):
         # to avoid problems in subsequent tests.
         del apps._pending_operations[('migrations', 'tribble')]
 
+    @override_settings(INSTALLED_APPS=['migrations.migrations_test_apps.unmigrated_app_syncdb'])
+    def test_migrate_syncdb_deferred_sql_executed_with_schemaeditor(self):
+        """
+        For an app without migrations, editor.execute() is used for executing
+        the syncdb deferred SQL.
+        """
+        with mock.patch.object(BaseDatabaseSchemaEditor, 'execute') as execute:
+            call_command('migrate', run_syncdb=True, verbosity=0)
+            create_table_count = len([call for call in execute.mock_calls if 'CREATE TABLE' in str(call)])
+            self.assertEqual(create_table_count, 2)
+            # There's at least one deferred SQL for creating the foreign key
+            # index.
+            self.assertGreater(len(execute.mock_calls), 2)
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_squashed"})
     def test_migrate_record_replaced(self):
         """