What happens if I rollback a transaction after I flush ? Does it roll back ?

My Problem is that I have a batch update process through my web app. And during that process I have to do session.flush() and session.clear() frequently. However the server sometimes crashes.

And I want to ensure that if server crashes the entire batch process is rolled back. How can I do it ?

Hi emperon,

In my experience, calling session.Flush() will do a Commit() for you. So I would answer, no you can't rollback a transaction after flushing.

[ed: NB I was absolutely wrong, it doesn't ;-0]

I think you are wrong. I am digging the issue. And I see flushing the session just runs the queries to be run on the database. But they still reside within the transaction. So YOU CAN ROLL BACK the transaction even if it is flushed.

Because basically flushing is the same as running the insert query (for e.g) by standard ado.net. And if you run an insert query within ado.net you can still roll it back safely. But I cannot speak for the impact of a transaction that has thousands of individual inserts.

Finally you know occasionally hibernate flushes the session by itself even if you do not flush it explicitly. If what you said were true , transactions would be completely pointless to use.

I think you're right. Although there's certainly some confused terminology in regards to this. For example, NHibernate in Action, says things like this:

We’ve noted that the call to Commit() synchronizes the ISession state with the database. This is called flushing, a process you automatically trigger when you use the NHibernate ITransaction API.

Flushing the ISession state to the database at the end of a database transaction is required in order to make the changes durable and is the common case

If flush() doesn't commit (I admit, if it did it would seem pointless), I still wish they wouldn't word things like that. It looks like they have a process called 'flushing' but which is not necessarily done by calling 'flush()'.

Still, I've learnt more by answering questions wrongly in the last few days, than I have in weeks of reading books. So thanks for putting up with me.

hehe no problem pal I am learning too. Btw why don't you come to IRC if you are so willing to discuss on nhibernate. irc.freenode.net #nhibernate. It's a ghost channel but I sometimes ask my hopeless questions there.