Issue #3498178: The key_value_sorted table does not have primar key thus will...

Issue #3498178: The key_value_sorted table does not have primar key thus will not work well with READ-COMMITTED transaction isolation level

Closes #3498178

key_value.install

 <?php
 
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+
 /**
  * Implements hook_schema().
  */
@@ -33,6 +35,18 @@ function key_value_schema() {
        'collection_name' => ['collection', 'name'],
        'name' => ['name'],
      ],
+    'primary key' => ['collection', 'name'],
   ];
   return $schema;
 }
+
+/**
+ * Add primary key to work with the READ COMMITTED transaction isolation level.
+ * @see https://www.drupal.org/docs/getting-started/system-requirements/setting-the-mysql-transaction-isolation-level
+ */
+function key_value_update_10100(&$sandbox = NULL): TranslatableMarkup {
+  $schema = \Drupal::database()->schema();
+  // Add primary key.
+  $schema->addPrimaryKey('key_value_sorted', ['collection', 'name']);
+  return \t('Added primary key to the key_value_sorted table.');
+}