@Override
  public void remove() {
    throw new UnsupportedOperationException();
  }
The MemStoreMergerSegmentsIterator extends MemStoreSegmentsIterator and performs the scan for
simple merge operation meaning it is NOT based on SQM
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreMergerSegmentsIterator.java