@Override
    public String toString() {
      StringBuilder sb = new StringBuilder();
      sb.append(super.toString());
      return sb.toString();
    }
Mark the key matched with equalKey as a match and read the set membership count,
if necessary.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/fast/VectorMapJoinFastBytesHashSetStore.java