public function __clone() {
        parent::__clone();

        $this->groupByColumnNames = ArrayHelper::copy($this->groupByColumnNames);
        $this->subjectColumnNames = ArrayHelper::copy($this->subjectColumnNames);
        $this->formattedGroupByColumnNames = ArrayHelper::copy($this->formattedGroupByColumnNames);
        $this->formattedSubjectColumnNames = ArrayHelper::copy($this->formattedSubjectColumnNames);
    }
    public function __clone() {
        parent::__clone();

        $this->keyColumnNames = ArrayHelper::copy($this->keyColumnNames);
    }
    public function __clone() {
        parent::__clone();

        $this->columnMappings = ArrayHelper::copy($this->columnMappings);
    }