public static BaseWork getMergeWork(Configuration jconf, String prefix) {
    if (StringUtils.isEmpty(prefix)) {
      return null;
    }

    return getBaseWork(jconf, prefix + MERGE_PLAN_NAME);
  }
ReduceField:
KEY: record key
VALUE: record value
ql/src/java/org/apache/hadoop/hive/ql/exec/Utilities.java