@Override
  public ExtendedCell next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    return kvsIterator.next();
  }
The MemStoreCompactorSegmentsIterator extends MemStoreSegmentsIterator and performs the scan for
compaction operation meaning it is based on SQM
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreCompactorSegmentsIterator.java