public boolean isOrderedAggregate() {
    return orderedAggregate;
  }
Property for indicating that the function is an Ordered-Set Aggregate function.
A WITHIN GROUP clause is required when invoked.
example:
SELECT rank(1) WITHIN GROUP (ORDER BY val) FROM t_table;
@return true if the function is a an Ordered-Set Aggregate function, false otherwise
ql/src/java/org/apache/hadoop/hive/ql/exec/WindowFunctionInfo.java