private static void replaceAlias(List<String> origin, List<String> cloned,
        String alias, String newAlias) {
      if (origin == null || cloned == null || origin.size() != cloned.size()) {
        return;
      }
      for (int i = 0; i < origin.size(); i++) {
        if (origin.get(i).equals(alias)) {
          cloned.set(i, newAlias);
        }
      }
    }
Set alias in the cloned join tree
ql/src/java/org/apache/hadoop/hive/ql/optimizer/SkewJoinOptimizer.java