Bulk insert or update with Hibernate?

There are many possible bottlenecks in to bulk operations. The best approach depends heavily on what your data looks like. Have a look at the Hibernate Manual section on batch processing.

At a minimum, make sure you are using the following pattern (copied from the manual):

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

for ( int i=0; i<100000; i++ ) {
Customer customer = new Customer(.....);
session.save(customer);
    if ( i % 20 == 0 ) { //20, same as the JDBC batch size
        //flush a batch of inserts and release memory:
        session.flush();
        session.clear();
    }
}

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

If you are mapping a flat file to a very complex object graph you may have to get more creative, but the basic principal is that you have to find a balance between pushing good sized chunks of data to the database with each flush/commit and avoiding exploding the size of the session level cache.

Lastly, if you don’t need Hibernate to handle any collections or cascading for your data to be correctly inserted, consider using a StatelessSession.