public int getDiff(Range prevRange) {
    return this.start - prevRange.start + this.end - prevRange.end;
  }
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