public String toString() {
    return String.format("Range: %d-%d, size: %d", start, end, getSize());
  }
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