Hibernate queries slow down drastically after an entity is loaded in the session

Question

I\'m using Hibernate EntityManager, and am experiencing a weird slowdown in my Hibernate queries. Take a look at this code:

public void testQuerySpeed() {
           


        

Answer 1

I also have to recommend using a JVM profiler to look at where the time is going. It also may not hurt to turn on the SQL statement logging for the Hibernate Session just to make sure that you're not running more SQL than you think you are.

The thing that first comes to mind here is the "flushing" behavior of the Hibernate Session. Do you explicitly set a specific flush mode on the Session? If not, then you get "auto" flushing which will do some amount of checking the objects you have in your session to determine whether or not there are changes in memory that need to be "flushed" back to the database (inside of a transaction, of course).

I guess the easiest thing to try first to see if it has any effect is to modify the test code you showed above to specify that you want flushing to occur manually when you commit your database transaction:

public void testQuerySpeed() {
    em.setFlushMode(FlushModeType.COMMIT); // assuming you're using JPA annotations
    CommercialContact contact = em.find(CommercialContact.class, 1890871l);

    for(int i = 0; i < 1000; i++) {
        em.createNativeQuery("SELECT 1").getSingleResult();
    }
}

Another thought I suppose would be to ask whether or not you can perform your bulk tasks in a separate EntityManager, which could work if you're just doing UPDATEs or INSERTs.