2960572-query-performance-flag.count: Reroll patch

Closes #2960572

src/Entity/Storage/FlaggingStorageSchema.php

@@ -18,6 +18,7 @@ class FlaggingStorageSchema extends SqlContentEntityStorageSchema {
 
     $schema['flagging']['indexes'] += [
       'entity_id__uid' => ['entity_id', 'uid'],
+      'flag_id__uid__session_id' => ['flag_id', 'uid', 'session_id'],
     ];
 
     return $schema;