[adding the mailing list] Generally speaking, looks like we agree on the direction: EntityEntry needs to be an interface, and some clever logic to select the appropriate implementations. In your draft you're having a single EntityEntryFactory as a global service; I'm wondering if we shouldn't have the possibiliy to have a different factory implementation per Entry type.. more on this below.
What is your primary differentiator between 'SharedEntityEntry' and 'StatefulEntityEntry' ? For our purposes I'd have used different names, but since there's no javadoc yet I wonder if you had different intentions. Personally I'd have chosen something like "ImmutableEntityEntry" and "MutableEntityEntry", there the Mutable one is a rename of the existing implementation, and the Immutable would be a slimmed down version which might not need fields such as: - loadedState (not needed for readonly) - version (what would be the point) - .. A concern I have is to avoid ever needing to "promote" an ImmutableEntityEntry into a MutableEntityEntry: it's easy to mark an existing instance of ImmutableEntityEntry as READ_ONLY, but there is no going back if the entity entry was initially loaded as READ_ONLY. One could think of swapping the existing entityentry, but that could get hairy and defeats the point of optimising object allocations. Is there a strong guarantee which we can rely on, that if an EntityEntry is marked READ_ONLY at first load, noone will ever need to re-mark it as mutable? If not, the current check in DefaultEntityEntryFactory basing the choice on the current status of the Entity might not be enough, we might need to be a bit more conservative and only based that on getPersister().isMutable() ? The READ_ONLY point which you're leveraging for this specific optimisation seems to be key for the specific optimisation we have in mind at this point; but generalizing the concept it seems to me that the choice of EE implementation to use for a specific Entity type will be a consistent choice for the lifecycle of the EntityPersister, and depending on immutable flags on the EntityPersister. Which is why I'm suggesting that the EntityPersister should have a dedicated EntityEntryFactory. Making the EntityEntryFactory a global service would force to go through all the checks of the EE implementation choice each time, while the choice should always be the same. I wouldn't argue to save a couple of simple "if" evaluations, but it's very possible that some more clever EntityEntryFactory implementations than this current draft might need to do more work, for example consult more Services to call back into OGM metadata. Not least, having a per-type EntityEntryFactory would make it possible to refer to it from some EntityEntry implementations and save some memory around the common state. Concurrency Since the goal is to share the ImmutableEntityEntry instance among multiple threads reading it, I'd rather make sure that it is really immutable. For example it now holds onto potentially lazy initialized fields, such as getEntityKey(). If it's not possible to make it really immutable (all final fields), we'll need to make it threadsafe and question the name I'm proposing. LockMode From a logical perspective of users, one might think that an entity being "immutable" doesn't necessarily imply I can't lock on it.. right? I'm not sure how far it could be a valid use case, but these patches are implying that one can't lock an immutable entity anymore, as the lock state would be as immutable as anything else on the EntityEntry. Are we good with that? Alternatively one might need to think to separate the lock state handling from the EntityEntry. On smaller details: # org.hibernate.engine.internal.SharedEntityEntry is hosted in an .internal package, I don't think it's right to refactor all the public API javadoc which was referring to EntityEntry to now refer to the internal implementation. # things like EntityEntryExtraState should probably get moved to .internal packages as well now - we couldn't do that before without breaking either encapsulation or APIs. In terms of git patches, the complexity of the changeset risks to get a bit our of hand. What about we focus on creating a clean pull request which focuses exclusively on making EntityEntry an interface, and move things to the right packages and javadoc? You'd have a trivial EntitEntryFactory, and we can then build the evolution on top of that, not least maybe helping out by challenging some points in parallel work. These are the things I'd leave for a second iteration: - add various implementations of EntityEntry iteratively, as needed - the strategy such a Factory would use the pick an implementation - ultimately, make it possible for an integrator to override such a Factory For example with Hibernate OGM we might want to override / re configure the factories to use custom EntityEntry implementations - requirements are not fully clear at this point but it seems likely. The priority being to define the API as that would be a blocker for 5.0, we have then better choices to leave more smarter and advanced EntityEntry implementations for the future; we'd still need to implement at least the essential ones to make sure the API of the EntityEntryFactory has all the context it needs. Thanks, Sanne On 24 March 2015 at 09:27, John O'Hara <joh...@redhat.com> wrote: > Steve, > > Have you had chance to look at this? Do you have any comments/observations? > > Thanks > > John > > > On 17/03/15 09:24, John O'Hara wrote: > > Steve, > > I have been having a think about the EntityEntry interface, and have forked > a branch here: > > https://github.com/johnaoahra80/hibernate-orm/tree/EntityEntryInterface > > I know it is nowhere near complete, but was this the sort of idea you had in > mind? > > Thanks > > John > > > On 13/03/15 09:44, John O'Hara wrote: > > EntityEntry retains a reference to a persistenceContext internally that > org.hibernate.engine.spi.EntityEntry#setReadOnly makes calls to, is this > where the session reference is kept? As > org.hibernate.engine.spi.PersistenceConext is an interface could we have a > different implementation for this use case? e.g. an > ImmutablePersistenceContext that could be shared across sessions? > > For the bytecode enhancement, could we change the enhancer so that it adds > an EntityEntry interface with javassist. > ClassPool.javassist.ClassPool.makeInterface()() as opposed to adding a class > javassist.ClassPool.makeClass()? I need to have a look at javassit to > confirm what javassist.ClassPool.makeInterface() does. > > Thanks > > John > > On 12/03/15 18:52, Steve Ebersole wrote: > > It is possible. Although some of the changes are particularly painful. > Most of EntityEntry, if it is an interface, can be made to work with your > use case. org.hibernate.engine.spi.EntityEntry#setReadOnly I think is the > one exception, because: > 1) your use case needs it > 2) it expects the Session to be available internally (its not passed) > > The bigger thing I am worried about for you is the bytecode stuff, as that > ties very tightly with EntityEntry. > _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
