presto-main/src/main/java/io/prestosql/execution/SqlTaskIoStats.java/SqlTaskIoStats/merge
class SqlTaskIoStats:    public void merge(SqlTaskIoStats ioStats)
    {
        inputDataSize.merge(ioStats.inputDataSize);
        inputPositions.merge(ioStats.inputPositions);
        outputDataSize.merge(ioStats.outputDataSize);
        outputPositions.merge(ioStats.outputPositions);
    }