public function addSummaryRow(Row $row)
    {
        $this->summaryRow = $row;

        // add summary row to index
        if (!$this->indexNotUpToDate
            && $this->rebuildIndexContinuously
        ) {
            $label = $row->getColumn('label');
            if ($label !== false) {
                $this->rowsIndexByLabel[$label] = self::ID_SUMMARY_ROW;
            }
        }

        return $row;
    }