Problem iterating through large query results

gab.co · **Joined:** Mon Dec 15, 2003 3:34 pm **Posts:** 18

Hi folks

I'm facing a severe situation with the following:

I must query thousands of objects and iterate through them all to do certain processing with each instance.

To achieve this I created a query:

Code:

Query query = session.createQuery("from Bill as b where b.date = ?");
query.setParameter(0, new Date());
Iterator results = query.iterate();

Then, for each iteration I must also create and persist a new instance of another bean:

Code:

while (results.hasNext()) {
   // do my processing ...
   Payment payment = new Payment();
   // set some payment's attribuites
   session.save(payment);
}

The first problem is that every instance loaded goes to the first level cache increasing the memory usage (about 62MB) until I get an OutOfMemoryException. To solve this I tried to evict each instance from the cache after using it, calling session.evict(), but the memory allocation continues to increase, though in a smaller rate (about 29MB), as I observed in W2K Task Manager.

The second problem is that the new instances of Payment also go to the cache and I would have the same problems to evict them.

Any comments will be wellcome.

Thanks.

gab.co · **Joined:** Mon Dec 15, 2003 3:34 pm **Posts:** 18

Hi again

I found a memory leak in my example:

The Bill bean had a many-to-one association with another bean and no "cascade" parameter in the mapping file. Once I specified cascade="all" for such association, evict() started to remove both objects from the first level cache keeping the memory usage stable.