I want to do a select for update NOWAIT with postgres. Postgresql is actually capable of this.

For NHibernate this is supported with NHibernate.Dialect.PostgreSQL81Dialect (https://www.hibernate.org/hib_docs/nhib ... ation.html). But for java-hibernate there is no PostgreSQL81Dialect (at least I cannot find anything about it).


session.lock( cleanupSaved, LockMode.UPGRADE_NOWAIT);

leads to this sql:

select ID from CLEANUP _TREE where ID =? for update

without NOWAIT.

I also fail to pass the 'for update nowait' together with hibernate statement

DAO.getUnique("from SessionTreeCleanup where id = ? for update nowait", cleanuptree.getId());
--> unexpected token: for near line 1, column 61 [from entities.CleanupTree where id = ? for update nowait]

What are my options when I need the nowait?

Thanks for your help

Yes, actually we're seeing the same symptom. Even though we pass UPGRADE_NOWAIT to session.get() it waits, which is kinda bad.

Should it throw an exception if UPGRADE_NOWAIT is not supported?

And, is there any way to patch in support for UPGRADE_NOWAIT for Postgres?

Thanks!

The problem is due to the fact that current version of Hibernate does not have nowait in its dialect, if you go have a look at the source code you will see that the methods that is supposed to append "for update nowait" string will instead delegate to the method that appends the regular string.

You can create your own dialect to solve the problem. See the following code



Don't forget to change the dialect class used in your persistence.xml settings.

I've solved the problem now by using native sql:

First I try if I can lock the row:


if I cannot lock it throws a GenericJDBCException that has nested another exception, whose message contains following text:



If I don't get the error, I just go on an get the thing via hibernate by id.

Especially the exception-thing is not beautful but it works at least for now.

But I will try the dialect-thing, perhaps I can use it on other places as well ...

Thanks