public function createIndex($name, $table, $columns, $unique = false)
    {
        $time = $this->beginCommand('create' . ($unique ? ' unique' : '') . " index $name on $table (" . implode(',', (array) $columns) . ')');
        $this->db->createCommand()->createIndex($name, $table, $columns, $unique)->execute();
        $this->endCommand($time);
    }