public IntWritable evaluate(RecordIdentifier i) {
    if (i == null) {
      return null;
    } else {
      BucketCodec decoder =
        BucketCodec.determineVersion(i.getBucketProperty());
      intWritable.set(decoder.decodeWriterId(i.getBucketProperty()));
      return intWritable;
    }
  }
Convert a RecordIdentifier.  This is done so that we can use the RecordIdentifier in place
of the bucketing column.
@param i RecordIdentifier to convert
@return value of the bucket identifier
ql/src/java/org/apache/hadoop/hive/ql/udf/UDFToInteger.java