protected static boolean[] getSortedTags(JoinOperator joinOp) {
    boolean[] result = new boolean[joinOp.getParentOperators().size()];
    for (int tag = 0; tag < result.length; tag++) {
      result[tag] = isSortedTag(joinOp, tag);
    }
    return result;
  }
@param operator the input operator
@param throwException if throw a exception when the input operator has multiple children
@return the single child or null when the input operator has multiple children and
        throwException is false;
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/optimizer/correlation/CorrelationUtilities.java