Hi all

I need to make a query that retrieve a large amount of records. I would like to know
how to minimise the memory footprint. I retrieved the data like the following.

Query query = session.createQuery("from account");
Iterator it = query.iterate();

while (it.hasNext()) {
Object o = it.next();
// ...
// ... use the object
// ...
session.evict(o);
it.remove();
}

When I run the program, the memory it uses keep growing and doesn't seem to release the memory of the object after use and eventually the program terminated with a OutOfMemoryError.

I tried removing the session.evict(o) and it.remove(), however the memory usage of the program is still the same.

How can the memory be released?

Thank in advance!!

Edmond

I don't know if Session.evict is cascade, that is if it evicts all dependent objects. But you can use Session.clear()

Session.evict() cascades to associations if they are mapped with cascade="all" or cascade="all-delete-orphan".

I think it should be added to the Session.evict javadoc :)

However, it throws OutOfMemoryError after getting almost the same amount of records no matter the Session.evict has been called or not. Therefore, I wonder if the object is still living in the iterator (or Collection), so even I called the evict there is still a reference of the object in the iterator (or Collection).


So, it can be solved??

Instead of Session.evict() use Session.clear(). Session.evict(obj) removes obj object and all its dependent ones mapped with cascade="all" and "all-delete-orphan". So if you have dirty objects in the Session cache, use:

else use only session.clear()

And add -Xms128m -Xmx512m to JVM options of your application server or Servlet/JSP container.