[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

django/db/backends/base/schema.py

@@ -2,7 +2,7 @@ import hashlib
 import logging
 from datetime import datetime
 
-from django.db.backends.utils import strip_quotes
+from django.db.backends.utils import split_identifier
 from django.db.models import Index
 from django.db.transaction import TransactionManagementError, atomic
 from django.utils import six, timezone
@@ -852,7 +852,7 @@ class BaseDatabaseSchemaEditor(object):
         The name is divided into 3 parts: the table name, the column names,
         and a unique digest and suffix.
         """
-        table_name = strip_quotes(model._meta.db_table)
+        _, table_name = split_identifier(model._meta.db_table)
         hash_data = [table_name] + list(column_names)
         hash_suffix_part = '%s%s' % (self._digest(*hash_data), suffix)
         max_length = self.connection.ops.max_name_length() or 200

django/db/backends/utils.py

@@ -4,7 +4,6 @@ import datetime
 import decimal
 import hashlib
 import logging
-import re
 from time import time
 
 from django.conf import settings
@@ -180,20 +179,35 @@ def rev_typecast_decimal(d):
     return str(d)
 
 
-def truncate_name(name, length=None, hash_len=4):
+def split_identifier(identifier):
     """
-    Shorten a string to a repeatable mangled version with the given length.
-    If a quote stripped name contains a username, e.g. USERNAME"."TABLE,
+    Split a SQL identifier into a two element tuple of (namespace, name).
+
+    The identifier could be a table, column, or sequence name might be prefixed
+    by a namespace.
+    """
+    try:
+        namespace, name = identifier.split('"."')
+    except ValueError:
+        namespace, name = '', identifier
+    return namespace.strip('"'), name.strip('"')
+
+
+def truncate_name(identifier, length=None, hash_len=4):
+    """
+    Shorten a SQL identifier to a repeatable mangled version with the given
+    length.
+
+    If a quote stripped name contains a namespace, e.g. USERNAME"."TABLE,
     truncate the table portion only.
     """
-    match = re.match(r'([^"]+)"\."([^"]+)', name)
-    table_name = match.group(2) if match else name
+    namespace, name = split_identifier(identifier)
 
-    if length is None or len(table_name) <= length:
-        return name
+    if length is None or len(name) <= length:
+        return identifier
 
-    hsh = hashlib.md5(force_bytes(table_name)).hexdigest()[:hash_len]
-    return '%s%s%s' % (match.group(1) + '"."' if match else '', table_name[:length - hash_len], hsh)
+    digest = hashlib.md5(force_bytes(name)).hexdigest()[:hash_len]
+    return '%s%s%s' % ('%s"."' % namespace if namespace else '', name[:length - hash_len], digest)
 
 
 def format_number(value, max_digits, decimal_places):

docs/releases/1.11.8.txt

@@ -15,3 +15,6 @@ Bugfixes
 * Added support for ``QuerySet.values()`` and ``values_list()`` for
   ``union()``, ``difference()``, and ``intersection()`` queries
   (:ticket:`28781`).
+
+* Fixed incorrect index name truncation when using a namespaced ``db_table``
+  (:ticket:`28792`).

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'))

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()