@SuppressWarnings("unchecked")
  @Override
  public RecordReader<NullWritable, NullWritable> getRecordReader(InputSplit split,
      JobConf conf, Reporter arg2) throws IOException {
    return new OneNullRowRecordReader(conf, split);
  }
OneNullRowInputFormat outputs one null row. Used in implementation of
metadata only queries.
ql/src/java/org/apache/hadoop/hive/ql/io/OneNullRowInputFormat.java