public void addPushDowns(String alias, List<ExprNodeDesc> pushDowns) {
    List<ExprNodeDesc> predicates = getPushdownPreds(alias);
    boolean isNew;
    for (ExprNodeDesc newPred: pushDowns) {
      isNew = true;
      for (ExprNodeDesc curPred: predicates) {
        if (curPred.isSame(newPred)) {
          isNew = false;
          break;
        }
      }
      if (isNew) {
        predicates.add(newPred);
      }
    }
  }
Adds the passed list of pushDowns for the alias.

@param alias
@param pushDowns
ql/src/java/org/apache/hadoop/hive/ql/ppd/ExprWalkerInfo.java