presto-main/src/main/java/io/prestosql/sql/planner/planprinter/WindowOperatorStats.java/WindowOperatorStats/mergeWith
class WindowOperatorStats:    @Override
    public WindowOperatorStats mergeWith(WindowOperatorStats other)
    {
        return new WindowOperatorStats(
                partitionRowsSumSquaredDiffs + other.partitionRowsSumSquaredDiffs,
                positionsInIndexesSumSquaredDiffs + other.positionsInIndexesSumSquaredDiffs,
                sizeOfIndexesSumSquaredDiffs + other.sizeOfIndexesSumSquaredDiffs,
                indexCountPerDriverSumSquaredDiffs + other.indexCountPerDriverSumSquaredDiffs,
                rowCountPerDriverSumSquaredDiffs + other.rowCountPerDriverSumSquaredDiffs,
                totalRowCount + other.totalRowCount,
                totalIndexesCount + other.totalIndexesCount,
                totalPartitionsCount + other.totalPartitionsCount,
                activeDrivers + other.activeDrivers,
                totalDrivers + other.totalDrivers);
    }