Another java.lang.OutOfMemory

spinodal · **Posted:** Tue Jan 18, 2005 11:54 am

Hibernate version: 2.1.6

Name and version of the database you are using: Oracle 10g

Mapping documents:

Code:

<class name="Category" table="CATEGORY">
   ...
   <property name="name" column="CATEGORY_NAME"/>
   <many-to-one
      name="parentCategory"
      class="Category"
      column="PARENT_CATEGORY_ID"
      cascade="none"/>
   <list
      name="childCategories"
      table="CATEGORY"
      cascade="all"
      inverse="true">
         <key column="PARENT_CATEGORY_ID"/>
     <index column="CATEGORY_CODE"/>
     <one-to-many class="Category"/>
   </list>
   ...
</class>

There are ~ 17500 total categories (actually it is not category in our application, I use category because there is a sample in Hibernate in Action like this, only difference is there was a set instead of list). When we try to load categories we always get "java.lang.outofmemoryerror". I know someone will send reply like
"Don't load all the table to session!".
But we are getting them to put into a dictionary to lookup in runtime (it will be used a lot and we don't want to go to database every time). We tried ScrollableResults and clearing session after every 20 category but result is same.

Is there a solution to this outofmemory problem?

Note: We searched the forum and read related posts (those we could find)

cardsharp · **Posted:** Tue Jan 18, 2005 2:00 pm

Try the approach mentioned in this blog:

http://blog.hibernate.org/cgi-bin/blosx ... batch.html

Basically, when you're iterating over large numbers of objects, you periodically need to flush and clear the session to prevent the caches from overflowing. As you can see in the blog posting, there is a very good reason for this.

cardsharp · **Posted:** Tue Jan 18, 2005 2:03 pm

In case the blog goes away or moves, just so the archive has the code, it goes something like:

Code:

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

ScrollableResults customers = session.getNamedQuery("GetCustomers")
   .scroll(ScrollMode.FORWARD_ONLY);
int count=0;
while ( customers.next() ) {
   Customer customer = (Customer) customers.get(0);
   customer.updateStuff(...);
   if ( ++count % 20 == 0 ) {
      //flush a batch of updates and release memory:
      session.flush();
      session.clear();
   }
}

tx.commit();
session.close();

cfsavant · **Joined:** Wed Feb 09, 2005 12:00 pm **Posts:** 2

Is there a way to programatically disable the cache. I don't want any objects cached while I perform bulk operations as the cache causes me more trouble than it is worth.

bestrafer · **Joined:** Wed May 11, 2005 5:39 am **Posts:** 9

try StatelessSession (has no persistence context )

amila733 · **Posted:** Thu May 24, 2007 6:40 am

Hi

Use lazy="true" in list element.

Amila
(Rate if helps)