Re: [hibernate-dev] JPA2 locking followup...

As I said on IRC, my belief is that we should expand this set of lock modes specifically to include NO_WAIT variants. Its really just a question of for which modes it makes sense. The spec says "javax.persistence.lock.timeout" is "defined by this specification for use in pessimistic locking" so obviously OPTIMISTIC and OPTIMISTIC_FORCE_INCREMENT are fine by themselves.

I don't think PESSIMISTIC_FORCE_INCREMENT needs a NO_WAIT variant, even if we were to support using this mode on non-versioned entities.

I am unclear yet whether PESSIMISTIC_READ will require a NO_WAIT variant.

Conversely for "with wait" semantics we will need to add support for the lock acquisition timeout. On Fri, 2009-10-30 at 13:49 -0400, Scott Marlow wrote: > How should we handle the _NOWAIT variants for the three Pessimistic > modes? The JPA2 style is to use the "javax.persistence.lock.timeout > (time in milliseconds, with 0 meaning no wait). > > Internally, we need Hibernate core to support the three pessimistic lock > modes (read, write, force_increment) with a JPA2 style timeout option. > Since, we need to support JPA2 timeout per requested lock, we might want > to support _NOWAIT via the same mechanism as we use for timeout. > > > On 10/30/2009 09:18 AM, Scott Marlow wrote: > >> For JPA2 support, I propose that Hibernate LockMode support the >> following equivalents of JPA2 LockModeType locks: >> >> >> LockMode.OPTIMISTIC (READ) >> LockMode.OPTIMISTIC_FORCE_INCREMENT (WRITE) >> LockMode.PESSIMISTIC_READ >> LockMode.PESSIMISTIC_WRITE >> LockMode.PESSIMISTIC_FORCE_INCREMENT >> >> Hibernate already supports NONE, so that doesn't need to be added. JPA2 >> defaults to LockModeType NONE. >> >> JPA1 READ + WRITE will be supported respectively via LockMode.OPTIMISTIC >> + LockMode.OPTIMISTIC_FORCE_INCREMENT. >> >> With this change, Hibernate (native (better term?)) applications would >> be able to request JPA2 like locks. This also means that JPA2 >> applications running with the Hibernate Entity Manager, will see similar >> locking behavior as native applications. >> >> Pros: >> >> - Application developers will have a consistent set of locking options >> in their JPA2 based applications and native Hibernate applications. >> >> - This helps the application developer to prepare their native Hibernate >> application to migrate to JPA2. >> >> Cons: >> >> - This ties Hibernate core locking internals to the JPA2 specification. >> As JPA continues to evolve, Hibernate core should follow in lockstep. >> Although, that is not a hard requirement. >> >> - An alternative would be introducing low level locking primitives that >> could be combined to support JPA2 style locks. I can explore this path >> if there is strong push back to the above proposal. >> >> Comments? >> >> Scott >> _______________________________________________ >> hibernate-dev mailing list >> hibernate-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hibernate-dev >> >> > _______________________________________________ > hibernate-dev mailing list > hibernate-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/hibernate-dev >