public function getRoot()
    {
        if ( $this->owner->{$this->parentIdField} ) {
            return Yii::$app->db->cache(function(){
                return call_user_func("$this->ownerClassName::findOne", current($this->getParentsId()));
            }, null, $this->getTagDependency());
        } else {
            return $this->owner;
        }
    }