public LongWritable evaluate(ShortWritable i) {
    if (i == null) {
      return null;
    } else {
      longWritable.set(i.get());
      return longWritable;
    }
  }
Convert from short to a long. This is called for CAST(... AS BIGINT)

@param i
         The short value to convert
@return LongWritable
ql/src/java/org/apache/hadoop/hive/ql/udf/UDFToLong.java