Re: [hibernate-dev] HHH-9701 - Develop "immutable EntityEntry" impl

I think there are two factors to consider, when the entity is marked as Immutable, and when the EntityEntry can be shared between sessions. Our use case concerns the ImmutableEntityEntry being cached and shared between sessions, so we need to check if the Entity is reference cached in the 2lc. Therefore I think the answer to the question below is; - I would consider the the trigger for using ImmutableEntityEntry when the Entity is marked as Immutable; - I would consider the trigger for not nulling the EntityEntry in the EntityEntryContext when the EntityEntry is an ImmutableEntityEntry and the Entity is reference cached in the 2lc There might be further optimizations for ImmutableEntityEntries that are not cached and shared between sessions that I am not aware of. It seems the most logical place to determine whether to create a MutableEntityEntry or an ImmutableEntityEntry is when a call is made to AbstractEntityPersister getEntityEntryFactory() and we can test to see if the Entity is Immutable. I was unsure how of the best method to determine if the Enity would be cached in the 2lc, so tested at the point EntityEntry is nulled in EntityEntryContext. removeEntityEntry() or EntityEntryContext.clear() On 10/04/15 17:46, Steve Ebersole wrote: To post my question again... It really depends on what y'all consider the trigger for using ImmutableEntityEntry. When would the EntityPersister use the EntityEntryFactory producing ImmutableEntityEntry instances? a) when the entity is marked immutable? b) when the entity is marked immutable *and* we need to cache it by reference? c) some other condition? Because the answer to this ^^ dictates how we need to check whether we can clear this reference On Fri, Apr 10, 2015 at 11:45 AM, Steve Ebersole <steve(a)hibernate.org&gt; wrote: > Well the performance is exactly what I had in mind when I asked you about > the exact "trigger for using ImmutableEntityEntry" in your use-case. > But you never replied to that. > > > > On Fri, Apr 10, 2015 at 9:26 AM, John O'Hara <johara(a)redhat.com&gt; wrote: > >> I have updated my current branch: >> https://github.com/johnaoahra80/hibernate-orm/tree/HHH-9701 >> >> - Extracted the deserialization of EntityEntry in EntityEntryContext >> into a separate method: >> https://github.com/johnaoahra80/hibernate-orm/commit/d9f5dc76e05a111d37db... >> - Created a LockModeException for invalid lock modes for an >> ImmutableEntity: >> https://github.com/johnaoahra80/hibernate-orm/commit/99e308ae267f9bfc3054... >> >> Do we need a new Exception type here, or could we just use a >> HibernateException with a message about invalid lock type? >> >> - Added a check when EntityEntryContext.clear() or EntityEntry. >> removeEntityEntry() is called to see if the EntityEntry is >> ImmutableEntityEntry AND the Entity is referenced cached in the 2lc: >> https://github.com/johnaoahra80/hibernate-orm/commit/310a2eb5b8988189806a... >> >> Not sure of the performance implications on this, I am planning a run on >> WF9 to test and regressions in our use case. >> >> - Extracted an AbstractEntityEntry superclass that >> MutableEntityEntry and ImmutableEntityEntry both inherit from: >> https://github.com/johnaoahra80/hibernate-orm/commit/df50d344441ed4cc8f3c... >> >> John >> >> >> >> >> On 07/04/15 20:20, Steve Ebersole wrote: >> >> TBH, I have no idea what happens to comments on a Pull Request when you >> squash and force push. >> >> I'd just leave the multiple commits. We can squash them later. >> >> On Tue, Apr 7, 2015 at 1:59 PM, John O'Hara <johara(a)redhat.com&gt; wrote: >> >>> Steve, >>> >>> I have made changes based on the github comments and your comments >>> below (https://github.com/johnaoahra80/hibernate-orm/commits/HHH-9701). >>> >>> Do you want me to squash the commits down to one? Not sure how this >>> would effect the comments you have already made on GH >>> >>> Thanks >>> >>> John >>> >>> >>> On 06/04/15 04:51, Steve Ebersole wrote: >>> >>> >>> >>> On Thu, Apr 2, 2015 at 4:45 AM, John O'Hara <johara(a)redhat.com&gt; wrote: >>> >>>> Steve, >>>> >>>> I have pushed a proposal for HHH-9701 to: >>>> https://github.com/johnaoahra80/hibernate-orm/tree/HHH-9701 >>>> >>>> There are a couple of areas that I would appreciate feedback; >>>> >>>> 1) Serialization/Deserialization - EntityEntries implementations can >>>> be serialized and each implementation provide their own serialization >>>> method. I have modified the serialization of EntityEntry in >>>> EntityEntryContext to write the Implementation class to the OutputStream so >>>> the correct class can be used to deserialize the object stream. Is the >>>> exception handling sufficient here, or do we need more robust handling of >>>> deserialization exceptions? : see >>>> https://github.com/johnaoahra80/hibernate-orm/commit/ec9b1fa3b97131ff1e65... >>>> >>> >>> I added some comments to that section. Also, overall I would extract >>> the deserialization bit into a separate method (deserializeEntityEntry). >>> >>> >>> >>> 2) In our (perf team) use case, we want to be able to share the >>>> ImmutableEntityEntry between sessions when they are referenced cached in >>>> the 2lc. I have modified EntityEntryContext to not null >>>> managedEntity.$$_hibernate_setEntityEntry if the EntityEntry is an instance >>>> of ImmutableEntityEntry. Do we need to add an extra checks here, to ensure >>>> that the entity is Reference Cached? I am not sure how we would test that >>>> case? : see >>>> https://github.com/johnaoahra80/hibernate-orm/commit/ec9b1fa3b97131ff1e65... >>>> >>> >>> It really depends on what y'all consider the trigger for using >>> ImmutableEntityEntry. When would the EntityPersister use the >>> EntityEntryFactory producing ImmutableEntityEntry instances? >>> a) when the entity is marked immutable? >>> b) when the entity is marked immutable *and* we need to cache it by >>> reference? >>> c) some other condition? >>> >>> I agree that we should only not clear that reference when the entity >>> is enabled for cache-by-reference. How that plays into this depends on the >>> answer to the above question. >>> >>> If (a), then I think that yes it makes sense to add a check to only >>> clear the ManagedEntity's EntityEntry reference if using cache-by-reference. >>> >>> If (b), then the EntiytPersister is only using the EntityEntryFactory >>> producing ImmutableEntityEntry instances when both are true. So the fact >>> that an entry is an instance of ImmutableEntityEntry indicates that we need >>> to not clear it from the ManagedEntity. >>> >>> >>> >>> >>>> 3) Lock Mode: Steve you mentioned about not doing locking for >>>> Immutable entities. Where is the locking implemented? Would it be >>>> sufficient to simply set the LockMode on the ImmutableEntityEntry to >>>> NONE/READ_ONLY when setLockMode is called? >>>> >>> >>> >>> Locking is implemented in many places. >>> >>> What I had in mind, in terms of implementation for EntityEntry, is >>> somewhat influenced by the choice between ignore versus exception in cases >>> where something is not supported. Basically I had thought to throw an >>> exception in ImmutableEntityEntry#setLockMode or to simply ignore the call >>> altogether. This is not a great solution. >>> >>> It is hard for me to justify ignoring the lock request in all cases. >>> What does everyone else think? >>> >>> >>> >>> >>> >>> -- >>> John O&#39;Harajohara(a)redhat.com >>> >>> JBoss, by Red Hat >>> Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. >>> Registered in UK and Wales under Company Registration No. 3798903 Directors: Michael Cunningham (USA), Charlie Peters (USA), Matt Parsons (USA) and Michael O'Neill (Ireland). >>> >>> >>> >> >> >> -- >> John O&#39;Harajohara(a)redhat.com >> >> JBoss, by Red Hat >> Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. >> Registered in UK and Wales under Company Registration No. 3798903 Directors: Michael Cunningham (USA), Charlie Peters (USA), Matt Parsons (USA) and Michael O'Neill (Ireland). >> >> >> > -- John O&#39;Harajohara(a)redhat.com JBoss, by Red Hat Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in UK and Wales under Company Registration No. 3798903 Directors: Michael Cunningham (USA), Charlie Peters (USA), Matt Parsons (USA) and Michael O'Neill (Ireland).