Statement.setFetchSize is not working properly

Question

I am using setFetchSize to limit the rows returned by query.
Here is Code without using setFetchSize -
Statement stmt = dao.createStatement();
ResultSet rset = stmt.executeQuery("SELECT * FROM temp"); 
while(rset.next ())
System.out.println( rset.getString (1) ); Code using setFetchSize -
Statement stmt = dao.createStatement();
stmt.setFetchSize(20);
ResultSet rset = stmt.executeQuery("SELECT * FROM temp"); 
while(rset.next ())
System.out.println( rset.getString (1) ); both the code returns same result. temp has has 50 records and all records are returned in both the cases.
Edited by: seeking_solution on Jul 22, 2009 5:25 AM

Answer 1

seeking_solution wrote:
Actually we have a process in which we process records from a table and send an email for each record.
This table can have >250,000 records. We create collection of VOs after getting record. Now having so many VOs in memory machine goes "out of Memory".
I want to fetch some number of records at a time then process them and send emails. then fetch next some number of records and perform processing on them.
Option 1
Process them in the database (probably much faster anyways.). Put a entry in a task table for each one processed. Use a sequential key of some sort (date or integer.) It also has a marker indicating whether notification has occurred. Your java app retrieves rows that do not have the marker set and can limit the number, which ordering via the sequential key allows. It sends and marks each as sent. It repeats until no rows left.
Option 2
Same as option 1 but you process in java. You still create the task table in the database, and send email just like in option 1.
Advantage of both of those is that you have an ongoing record of completion (row itself) and notification (which can include a timestamp.)