@Override
  protected int compareFamilies(KeyValue left, int leftFamilyPosition, int leftFamilyLength,
    KeyValue right, int rightFamilyPosition, int rightFamilyLength) {
    return leftFamilyLength - rightFamilyLength;
  }
Compare two HBase cells inner store, skip compare family for better performance. Important!!! we
should not make fake cell with fake family which length greater than zero inner store, otherwise
this optimization cannot be used.
hbase-common/src/main/java/org/apache/hadoop/hbase/InnerStoreCellComparator.java