protected MemStoreCompactor createMemStoreCompactor(MemoryCompactionPolicy compactionPolicy)
    throws IllegalArgumentIOException {
    return new MemStoreCompactor(this, compactionPolicy);
  }
Types of indexes (part of immutable segments) to be used after flattening, compaction, or merge
are applied.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CompactingMemStore.java