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

[Steve Ebersole]

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 at redhat.com> 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 at redhat.com> 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/ec9b1fa3b97131ff1e65a1cc30ff6e4f2d2c8a28#diff-b55e1e51b30abe8d3c280bb22aeb6a44R380
>>
>
>  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/ec9b1fa3b97131ff1e65a1cc30ff6e4f2d2c8a28#diff-b55e1e51b30abe8d3c280bb22aeb6a44L281
>>
>
>  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'Harajohara at redhat.com
>
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