Ref Cursors / throwing data into a Ref Cursor as data is fetched

Question

I was wondering if anyone has executed an SQL statement and as each row is being fetched back from an SQL, doing some data checks and processing to see if the row is valid to return or not, based on the values being fetched in an SQL.
For example, I'm taking an SQL statement and trying to do some tuning. I have an Exists clause in the Where statement that has a nested sub-query with some parameters passed in. I am attempting to move that statement to a function call in a package (which is called in the SELECT statement). As I fetch each row back, I want to check some values that are Selected and if the values are met, then, I want to execute the function to see if the data exists. If it does exist, then, I want the fetched row returned in the Ref Cursor. If the criteria is met and the row doesn't exist in the function call, then, I don't want the fetched row to return.
Right now, the data has to be thrown to REF Cursor because it's being outputted to the Java application as a Result Set.
I've found many statements where you can take a SELECT statement and throw the Results in the Ref Cursor. But, I want to go a step further and before I throw each row in the Ref Cursor, I want to some processing to see if I put the Fetched Row in the Ref Cursor.
If someone has a better idea to accomplish this, I'm all ears. Like I say, I'm doing this method only for the sake of doing some database tuning and I think this will speed things up. Having the EXISTS clause works and it runs fast from an End-user standpoint but, when it processes on the database with the nested subquery, it is slow.
Here's an example of something that might be a problem (Notice the nested subquery). I moved the nested subquery to a function call written on the database package and make the call to the procedure/package in the SELECT statement. As I process each row, I want to check some values prior having the function call execute. If it meet some criteria, then the record is Ok to fetch and display in the Ref Cursor. If it does not meet the criteria and goes through the function and doesn't return data, then, I don't want the Fetched row from the main query to return the data.:
SELECT EMPNO,
FIRST_NAME,
LAST_NAME
FROM EMP E,
DEPT D
WHERE E.DEPTNO = D.DEPTNO
AND EXISTS (SELECT 'X'
FROM MANAGER M
WHERE M.MANAGER_ID = E.MANAGER_ID
AND MANAGER_TYPE IN (SELECT MANAGER_TYPE
FROM MANAGER_LOOKUP ML WHERE ML.MANAGER_TYPE = M.MANAGER_TYPE))
Any help or ideas of other things to try is appreciated. Keep in mind that I am returning this data to the Java application so, throwing the data to a Ref Cursor in the PL/SQL is the ideal method.
Chris

Answer 1

Ref cursors are not required nor desirable when writing java database application. Cursors are mentioned only once in the JDBC documentation reference guide, in the section "Memory Leaks and Running Out of Cursors".
In a word cursors are just plain ridiculous, and in fact I never used them in my 15+ years of application development practice:
http://vadimtropashko.wordpress.com/cursors/