@Override
  public boolean equals(Object obj) {
    if (!(obj instanceof JoinCondDesc)) {
      return false;
    }

    JoinCondDesc other = (JoinCondDesc) obj;
    if (this.type != other.type || this.left != other.left ||
      this.right != other.right || this.preserved != other.preserved) {
      return false;
    }
    return true;
  }
@param preserved
         if table is preserved, false otherwise
ql/src/java/org/apache/hadoop/hive/ql/plan/JoinCondDesc.java