Re: [hibernate-dev] PESSIMISTIC_FORCE_INCREMENT lock mode

Hey, I'm still a bit uncertain about this, as I only tested this lock mode with H2 which as far as I know is not supporting shared locks, so it will automatically acquire an exclusive lock. That is a possibility why I've seen the FOR UPDATE clause at the end of the SELECT statement. *My question rather is:* what's the intended behavior of this lock mode? Okay, it's a pessimistic lock with incrementing the version number automatically at locking time. What type of lock will it acquire? Shared or exclusive? I think this is important and it should be really mentioned in the Hibernate docs as now it's a bit confusing. The JPA spec is also unclear for me about this lock mode. Thank you guys for helping me out! Best Regards, Arnold On Fri, Jul 28, 2017 at 7:40 AM, Vlad Mihalcea <mihalcea.vlad(a)gmail.com&gt; wrote: > 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(a)gmail.com&gt; 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-patter >> ns-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 >> _______________________________________________ >> hibernate-dev mailing list >> hibernate-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hibernate-dev >> > >