public static boolean needsTagging(ReduceWork rWork) {
    return rWork != null && (rWork.getReducer().getClass() == JoinOperator.class ||
         rWork.getReducer().getClass() == DemuxOperator.class);
  }
General utility common functions for the Processor to convert operator into
map-reduce tasks.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/GenMapRedUtils.java