Hibernate is slow without calling Evict()

prince0 · **Joined:** Wed May 23, 2007 4:09 am **Posts:** 16

In a loop (let say 1000 iterations)
1) if I make just one query (session.CreateQuery()), it's fast
2) if I make just an insert (session.Save()), it's fast

but if I do both in my loop, hibernate is very very slow.

This is true with any database but it doesn't occur with other ORM or with a native ADO.NET code.

It seems the method session.Evict() fix the issue.

Dos anyone have an explanation or advices?
Thanks in advance.

Example:

Code:

for(int i=0; i<1000; i++)
{
    session.CreateQuery("from Test where name=?")
        .SetString(0, "hello")
        .UniqueResult();

    MyObj obj = new MyObj();
    session.SaveOrUpdate(obj);

    // This makes execution fast but why?
    // How can I avoid making this call?
    session.Evict(obj);
}

Please notice this occurs event with 10 iterations, and this does not occur if I do 2 loops.

Exemple of fast code running without problem:

Code:

for(int i=0; i<1000; i++)
{
    session.CreateQuery("from Test where name=?")
        .SetString(0, "hello")
        .UniqueResult();
}
for(int i=0; i<1000; i++)
{
    MyObj obj = new MyObj();
    session.SaveOrUpdate(obj);
}

VampBoy · **Posted:** Thu Jul 26, 2007 11:37 am

When you save an object you are locking it into the session. When you execute a query Hibernate by default will check your objects to see if you have made any changes to them (AutoFlush behaviour).

Evicting the object removes it from the session (1st level cache) so Hibernate no longer needs to keep track of it.

If you know for a fact that you're not updating the same tables you are selecting from you should be able to get the same order of performance by setting session.setFlushMode(FlushMode.MANUAL)

Bear in mind that when you do this you will need to manually flush your session so that your saved objects are sent to the DB.