[hibernate-dev] Should EntityManager#refresh retain an existing lock?

[Sanne Grinovero]

Hi Gail,

personally I wouldn't expect the pessimistic lock to be dropped.
In case of optimistic locking, I would expect the version to be
updated to the latest read  - the one triggered by the refresh.

I just read section 3.4 as you suggested but I couldn't find were it
suggests that "a lock on an entity should be dropped when refreshed" ;
what makes you think it indicates that?

On the other hand, section 3.4.3 is quite explicit about no other
changes being allowed by other transactions until the end of the
transaction, which I guess makes sense.

Would it even be possible to "unlock" a row on which we have a
pessimistic lock without committing the transaction? I don't think
that's possible, so that should clarify what needs to be done.

Thanks,
Sanne



On 31 January 2018 at 20:51, Gail Badner <gbadner at redhat.com> wrote:
> HHH-12257 involves refreshing an entity that is already has a pessimistic
> lock. In the test case attached to the jira, EntityManager#refresh(Object
> entity) is used to refresh the entity, instead of a method that specifies a
> particular LockModetype (e.g., #refresh(Object entity, LockModeType
> lockMode)). The lock on the refreshed entity is dropped.
>
> A workaround is to determine the current lock mode using
> Session#getCurrentLockMode, which returns a org.hibernate.LockMode object,
> which can be converted to a LockModeType that can be used to call
> EntityManager#refresh(Object entity, LockModeType lockMode).
>
> Unfortunately, the code that converts org.hibernate.LockMode to
> LockModeType is "internal" (org.hibernate.internal.util.LockModeConverter).
>
> I'm on the fence about how this should work.
>
> The API for EntityManager#refresh(Object entity)  does not say that an
> existing lock mode on the entity should be retained.
>
> On the other hand, in JPA 2.1 spec, 3.4 Locking and Concurrency section
> seems to indicate that locks on an entity apply to the transaction, and
> does say that a lock on an entity should be dropped when refreshed without
> an specified LockModeType.
>
> Does anyone have any guidance on how this should work?
>
> Thanks,
> Gail
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