Hello,

I have acquired a lock on an object using Session.lock(obj, LockMode.UPGRADE) to prevent other transactions from writing to this object.

Is it possible to release this lock explicitely *before* the end of the transaction? I have tried Session.lock(obj, LockMode.NONE), but that seems to do nothing.

Thanks for any help.

Uhm, if you obtain a row-level exclusive write lock in the database, you do so because you say "I want to make sure that nobody writes to this while I do". If you would be able to (you can't) release the lock before the end of your transaction, the whole exercise would be futile.

Thank you for the quick reply.

What I wanted to do is this: I want to read an object graph (a parent object plus several connected objects) in a consistent state, i.e. once I begin reading the object graph no other transaction should be able to write to any of those objects until I finish reading them.

The idea was to set a lock on the parent object, read the objects, then release the lock.

Any transaction that wants to write any object of this graph has to lock the parent object first. That way I would prevent any object of the graph from being modified while another transaction is reading.

One more question about not being able to release locks: is this a restriction of Hibernate or is this generally impossible on the database side?

Maybe a nested transaction would do the trick - then the lock would be released at the end of the inner transaction, wouldn't it?

Thanks for any more insights.

SQL can't do it and also Java (as in JDBC and JTA) doesn't support nested transactions. Some DBMS might have a proprietary SQL command for lock release though. Keep in mind that many DBMS already provide repeatable read, even if they are in read committed mode (Oracle, PostgreSQL, SQL Server 2005, basically any MVCC-capable database).