presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/util/ConcatPageSource.java/ConcatPageSource/getCompletedBytes
class ConcatPageSource:    @Override
    public long getCompletedBytes()
    {
        setup();
        return completedBytes + ((current != null) ? current.getCompletedBytes() : 0);
    }