private static String toUTF8(Object o) {
    if(o == null || o instanceof NullWritable) {
      return "\\N"; /* as found in LazySimpleSerDe's nullSequence */
    }
    return o.toString();
  }
Return count of qualifying rows.

@return number of rows that have not been filtered out
storage-api/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizedRowBatch.java