[1.11.x] Fixed #28792 -- Fixed index name truncation of namespaced tables.

Refs #27458, #27843.

Thanks Tim and Mariusz for the review.

Backport of ee85ef8315db839e5723dea19d8b971420a2ebb4 from master

2 files changed, 32 insertions, 1 deletions

diff --git a/tests/backends/test_utils.py b/tests/backends/test_utils.py
index 47720f7c92..6fac407a6e 100644
--- a/tests/backends/test_utils.py
+++ b/tests/backends/test_utils.py
@@ -1,5 +1,5 @@
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends.utils import truncate_name
+from django.db.backends.utils import split_identifier, truncate_name
 from django.db.utils import load_backend
 from django.test import SimpleTestCase
 from django.utils import six
@@ -25,3 +25,9 @@ class TestLoadBackend(SimpleTestCase):
         self.assertEqual(truncate_name('username"."some_table', 10), 'username"."some_table')
         self.assertEqual(truncate_name('username"."some_long_table', 10), 'username"."some_la38a')
         self.assertEqual(truncate_name('username"."some_long_table', 10, 3), 'username"."some_loa38')
+
+    def test_split_identifier(self):
+        self.assertEqual(split_identifier('some_table'), ('', 'some_table'))
+        self.assertEqual(split_identifier('"some_table"'), ('', 'some_table'))
+        self.assertEqual(split_identifier('namespace"."some_table'), ('namespace', 'some_table'))
+        self.assertEqual(split_identifier('"namespace"."some_table"'), ('namespace', 'some_table'))
diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 671e1234ff..8e868dfb0e 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -2267,6 +2267,31 @@ class SchemaTests(TransactionTestCase):
             cast_function=lambda x: x.time(),
         )
 
+    @isolate_apps('schema')
+    def test_namespaced_db_table_create_index_name(self):
+        """
+        Table names are stripped of their namespace/schema before being used to
+        generate index names.
+        """
+        with connection.schema_editor() as editor:
+            max_name_length = connection.ops.max_name_length() or 200
+            namespace = 'n' * max_name_length
+            table_name = 't' * max_name_length
+
+            class TableName(Model):
+                class Meta:
+                    app_label = 'schema'
+                    db_table = table_name
+
+            class NameSpacedTableName(Model):
+                class Meta:
+                    app_label = 'schema'
+                    db_table = '"%s"."%s"' % (namespace, table_name)
+            self.assertEqual(
+                editor._create_index_name(TableName, []),
+                editor._create_index_name(NameSpacedTableName, []),
+            )
+
     @unittest.skipUnless(connection.vendor == 'oracle', 'Oracle specific db_table syntax')
     def test_creation_with_db_table_double_quotes(self):
         oracle_user = connection.creation._test_database_user()