@Override
  public boolean isSloppy() {
    return true;
  }
This method is called before the flush is executed.
@return an estimation (lower bound) of the unflushed sequence id in memstore after the flush is
        executed. if memstore will be cleared returns {@code HConstants.NO_SEQNUM}.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CompactingMemStore.java