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

Fri Apr 10 12:46:21 EDT 2015

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 at hibernate.org>
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 at redhat.com> 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/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> 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
>>>
>>> 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'Harajohara 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).
>>
>>
>>
>