long stampRegionSequenceId(MultiVersionConcurrencyControl.WriteEntry we) throws IOException {
    long regionSequenceId = we.getWriteNumber();
    if (!this.getEdit().isReplay() && inMemstore) {
      for (Cell c : getEdit().getCells()) {
        PrivateCellUtil.setSequenceId(c, regionSequenceId);
      }
    }

    getKey().setWriteEntry(we);
    return regionSequenceId;
  }
Here is where a WAL edit gets its sequenceid. SIDE-EFFECT is our stamping the sequenceid into
every Cell AND setting the sequenceid into the MVCC WriteEntry!!!!
@return The sequenceid we stamped on this edit.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/FSWALEntry.java