[1.11.x] Refs #28876 -- Fixed incorrect foreign key constraint name for models with quoted db_table.

Thanks Simon Charette and Tim Graham for the review and Carlos E. C.
Leite for the report.

Backport of fc48047586a8f92262f55d9d2bfb976325844b23 from master

django/db/backends/base/schema.py

@@ -951,7 +951,7 @@ class BaseDatabaseSchemaEditor(object):
     def _create_fk_sql(self, model, field, suffix):
         from_table = model._meta.db_table
         from_column = field.column
-        to_table = field.target_field.model._meta.db_table
+        _, to_table = split_identifier(field.target_field.model._meta.db_table)
         to_column = field.target_field.column
         suffix = suffix % {
             "to_table": to_table,
@@ -962,7 +962,7 @@ class BaseDatabaseSchemaEditor(object):
             "table": self.quote_name(from_table),
             "name": self.quote_name(self._create_index_name(model, [from_column], suffix=suffix)),
             "column": self.quote_name(from_column),
-            "to_table": self.quote_name(to_table),
+            "to_table": self.quote_name(field.target_field.model._meta.db_table),
             "to_column": self.quote_name(to_column),
             "deferrable": self.connection.ops.deferrable_sql(),
         }

docs/releases/1.11.9.txt

@@ -14,3 +14,6 @@ Bugfixes
 
 * Fixed incorrect class-based model index name generation for models with
   quoted ``db_table`` (:ticket:`28876`).
+
+* Fixed incorrect foreign key constraint name for models with quoted
+  ``db_table`` (:ticket:`28876`).

tests/schema/tests.py

@@ -1784,6 +1784,28 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor() as editor:
             editor.add_field(BookWithLongName, new_field)
 
+    @isolate_apps('schema')
+    @skipUnlessDBFeature('supports_foreign_keys')
+    def test_add_foreign_key_quoted_db_table(self):
+        class Author(Model):
+            class Meta:
+                db_table = '"table_author_double_quoted"'
+                app_label = 'schema'
+
+        class Book(Model):
+            author = ForeignKey(Author, CASCADE)
+
+            class Meta:
+                app_label = 'schema'
+
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+            editor.create_model(Book)
+        if connection.vendor == 'mysql':
+            self.assertForeignKeyExists(Book, 'author_id', '"table_author_double_quoted"')
+        else:
+            self.assertForeignKeyExists(Book, 'author_id', 'table_author_double_quoted')
+
     def test_add_foreign_object(self):
         with connection.schema_editor() as editor:
             editor.create_model(BookForeignObj)