private Set<Operator<?>> getDirectWorks(Collection<List<Operator<?>>> values) {
    Set<Operator<?>> operators = new HashSet<Operator<?>>();
    for (List<Operator<?>> works : values) {
      for (Operator<?> work : works) {
        if (work != null) {
          operators.add(work);
        }
      }
    }
    return operators;
  }
@param aliasToFetchWork
         the aliasToFetchWork to set
ql/src/java/org/apache/hadoop/hive/ql/plan/MapredLocalWork.java