[hibernate-dev] PESSIMISTIC_FORCE_INCREMENT lock mode

[Vlad Mihalcea]

That's how Hibernate was executing the statements when I wrote the article.

I spotted the difference when writing the book, but didn't have time to
update the article.
I changed the SQL output to reflect the current behavior which adds a FOR
UPDATE clause when fetching the entity.

I also rephrased that sentence since it's no longer relevant to the current
behavior.

Vlad

On Thu, Jul 27, 2017 at 4:46 PM, Arnold Gálovics <galovicsarnold at gmail.com>
wrote:

> Hi all,
>
> I'm a bit confused with the mentioned lock mode.
>
> *The doc says the following:*
> *"The entity is locked pessimistically and its version is incremented
> automatically even if the entity has not changed."*
>
> I'm checking this with an H2 DB and the current behavior is the following:
> - the version attribute is incremented in advance, right after fetching
> (I'm using EntityManager#find here, but with lock, it should be the same)
> - the original fetching query contains the SELECT ... FOR UPDATE clause
>
> Knowing this, it seems for me that this lock mode involves a DB lock,
> however the doc doesn't say anything about this, especially whether it's a
> shared or exclusive lock.
>
> I've checked Vlad's article about this.
> https://vladmihalcea.com/2015/02/16/hibernate-locking-
> patterns-how-does-pessimistic_force_increment-lock-mode-work/
>
> It says the following: "*The PESSIMISTIC_FORCE_INCREMENT naming might lead
> you into thinking that you are using a pessimistic locking strategy, while
> in reality this Lock Mode is just an optimistic locking variation."*
>
> So now I'm unsure what this really is.
>
> Could you please briefly describe it to me if I missed something?
>
> Thanks in advance!
>
> Best Regards,
> Arnold
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