Fixed #14180 -- Prevented unneeded index creation on MySQL-InnoDB

Thanks zimnyx for the report and Simon Charette, Tim Graham for
the reviews.

1 files changed, 15 insertions, 1 deletions

diff --git a/tests/indexes/tests.py b/tests/indexes/tests.py
index 86000bb94c..0710446245 100644
--- a/tests/indexes/tests.py
+++ b/tests/indexes/tests.py
@@ -5,7 +5,7 @@ from django.db import connection
 from django.test import TestCase
 from django.test.utils import IgnorePendingDeprecationWarningsMixin
 
-from .models import Article, IndexTogetherSingleList
+from .models import Article, ArticleTranslation, IndexTogetherSingleList
 
 
 class CreationIndexesTests(IgnorePendingDeprecationWarningsMixin, TestCase):
@@ -82,3 +82,17 @@ class SchemaIndexesTests(TestCase):
         """Test indexes are not created for related objects"""
         index_sql = connection.schema_editor()._model_indexes_sql(Article)
         self.assertEqual(len(index_sql), 1)
+
+    @skipUnless(connection.vendor == 'mysql', "This is a mysql-specific issue")
+    def test_no_index_for_foreignkey(self):
+        """
+        MySQL on InnoDB already creates indexes automatically for foreign keys.
+        (#14180).
+        """
+        storage = connection.introspection.get_storage_engine(
+            connection.cursor(), ArticleTranslation._meta.db_table
+        )
+        if storage != "InnoDB":
+            self.skip("This test only applies to the InnoDB storage engine")
+        index_sql = connection.schema_editor()._model_indexes_sql(ArticleTranslation)
+        self.assertEqual(index_sql, [])