@Override
  public int hashCode() {
    int hash = 1;
    hash = 31 * hash + end;
    if (p != null){
      hash = 31 * hash + p.hashCode();
    }
    return 31 * hash + start;
  }
When there are no parameters specified, partition iterator can be made faster;
In such cases, it need not materialize the ROW from RowContainer. This saves lots of IO.
ql/src/java/org/apache/hadoop/hive/ql/udf/ptf/Range.java