[hibernate-dev] HHH-9701 - Develop "immutable EntityEntry" impl
John O'Hara
johara at redhat.com
Fri Apr 10 10:26:41 EDT 2015
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/d9f5dc76e05a111d37dbdac64c6aa1bd485a1ba9
* Created a LockModeException for invalid lock modes for an
ImmutableEntity:
https://github.com/johnaoahra80/hibernate-orm/commit/99e308ae267f9bfc30547784087955d7dc1e73e0
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/310a2eb5b8988189806a2e688090a7ea16ae5474
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/df50d344441ed4cc8f3c3c8df90edc106dd52adb
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 at redhat.com
> <mailto: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
>> <mailto: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'Hara
> johara at redhat.com <mailto:johara at redhat.com>
>
> JBoss, by Red Hat
> Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom.
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>
>
--
John O'Hara
johara at 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).
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