How to fetch some certain records at a time

Question

Hi everyone,
I dont know how to fetch some records at a time,
for some reason,there is not enouht memory.so I cant
fethch all the records at a time.
example, every time I only want to fetch 10
records. Does anyone know that?
thanks
Krussi

Answer 1

I think you may be getting setFetchSize(int) and setMaxRows(int) confused. I may have added to the confusion with my breaking out of the loop comment.
setFetchSize(int) gives the driver a hint as to how many rows it should store in memory at a time internally, ie. within the driver. It has no real effect on how you write your program at all. Its only purpose is to limit memory usage by the driver. To limit the rows returned, use setMaxRows.
For example, assume a result set has 20 rows and you use:
rs.setFetchSize(5);
while (rs.next()) {
   System.out.println("Rows: " + (++count));
}  You still get a count from 1 to 20. However, internally the driver is only holding in memory 5 records at a time, after the 5 returned it will discard those and get the next 5. So instead of holding 20 rows, its only holding 5 at a time. If you change rs.setFetchSize(5) to rs.setMaxRows(5) you will only get a count from 1 to 5, the rest are silently discared and rs.next() returns false.
Check your documentation to see if your driver supports the method. I believe many drivers don't. If not, I believe there is no way around multiple queries. Even if there is no rowid, as long as you order your queries you should be able to start again where you left off.
Disclaimer: Both drivers I commonly use do not implement setFetchSize(int). Someone let me know if I've fudged something here.
Good Luck