How can I flush the session cache?

Lasek · **Joined:** Fri Apr 29, 2005 10:57 pm **Posts:** 41

My understanding is calling Session.flush() will cause it to commit transaction, but what if I want to flush the session's cache? As a matter of fact, what if I want to disable that cache completely?

It's just that the program I'm working on stores huges amounts of data into database, but it's not performance-focused, so I chose to use Hibernate, but I'm worried that it will keep storing up stuff in session's cache and give me an out of memory exception..

thanks!

aabeling · **Posted:** Wed Jul 20, 2005 6:34 am

The javadoc of Session.flush() says

Quote:

Force the Session to flush. Must be called at the end of a unit of work, before commiting the transaction and closing the session (Transaction.commit() calls this method). Flushing is the process of synchronising the underlying persistent store with persistable state held in memory.

So it is just the other way round: the commit includes Session.flush()

You cannot disable the first-level-cache (the Session).

If you want to clear the first-level-cache use Session.clear().

Lasek · **Joined:** Fri Apr 29, 2005 10:57 pm **Posts:** 41

Oh thanks!

Is there any documentation on how big the session cache will grow? Maybe I won't have to do it at all..

aabeling · **Posted:** Thu Jul 21, 2005 2:13 am

According to this article from Gavin the size of the Session is not limited:

http://blog.hibernate.org/cgi-bin/blosxom.cgi/Gavin%20King/batch.html

wad · **Posted:** Thu Aug 11, 2005 3:08 pm

I'm running into memory problems, and this older thread might be a place to discuss.

My program chews through a large database, and verifies a bunch of data. I never commit anything. I would love to disable the cache, but it seems I cannot. So instead, I implemented the Session.clear() as described in this thread.

Guess what? It doesn't help at all. I run out of memory, whether or not I call that clear() method between batches of records.

I ran it with a profiler (JMP) and the usage doesn't even dip when that is called.

Any ideas?

wad · **Posted:** Thu Aug 11, 2005 3:16 pm

Okay, I guess I should have read that post from Gavin (linked above) before posting. I added a Session.flush() to my existing Session.clear(). We'll try that out now...

Lasek · **Joined:** Fri Apr 29, 2005 10:57 pm **Posts:** 41

Also don't forget to consider the option that it might not be Hibernate but your program :)

When working with large chunks of data don't forget to nullify references... I am not sure if calling garbage collect method does anything...