[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3910) Add support for custom dirty checking during flush

[Shawn Clowater (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33188#action_33188 ] 

Shawn Clowater commented on HHH-3910:
-------------------------------------

Yeah, I think i might have screwed that up when I put it back to what I initially tried.

I originally had what I posted before I did the patch

return isMutableInstance && getPersister().isDirtyCheckRequired(entity) && (
getPersister().hasMutableProperties() ||
!FieldInterceptionHelper.isInstrumented( entity ) ||
FieldInterceptionHelper.extractFieldInterceptor( entity).isDirty()
); 

My thoughts were that if it wasn't dirty from me tagging it as such then I don't want to continue to even check.

The way you have it, it's going to return true any time you have a mutable property and that's essentially always going to return true for any entity with updatable properties so it's not really going to buy you anything except bypass the instrumentation call but I'm not sure that is even valid as it can be dirty as well.

I don't have a standalone test case right now but I can maybe do one up in a couple of days, I'm not even sure I understand what's going on since the code that was failing on my side is wrapped up in some rather convoluted logic.



> Add support for custom dirty checking during flush
> --------------------------------------------------
>
>                 Key: HHH-3910
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3910
>             Project: Hibernate Core
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 3.3.1
>            Reporter: Ovidio Mallo
>         Attachments: DirtyCheckFailedAttempt.patch
>
>
> Currently, Hibernate supports a special dirty checking on instrumented entities
> in order to improve the flush performance. IMO, this optimization can often be
> rather significant. However, the drawback is that you have to use bytecode
> instrumentation in order to take advantage of this performance improvement which
> might not be an option in some projects.
> Therefore, I wanted to propose to extend the current dirty checking during flush
> in such a way that the dirtyness information can also be directly provided by
> clients. Thereby, I could think of two possible approaches to do this:
> 1. Introduce an interface which client entities might implement in case they
>    have some notion of dirtyness. The interface could look something like:
>      public interface DirtyAwareEntity {
>        boolean getMightBeDirty();
>        void setMightBeDirty(boolean mightBeDirty);
>      }
>    Using such an interface, Hibernate could easily check whether an entity might
>    be dirty during flush and it could also reset the dirty flag after flush just
>    as is currently done for instrumented classes. So this approach would probably
>    be rather easy to implement and very convenient for clients since they would
>    only have to implement that interface on the appropriate entities and set the
>    dirty flag when the entity is actually modified.
> 2. Add some hooks on event listeners and/or on the Interceptor for querying whether
>    an entity is dirty and for resetting the dirty flag. E.g. one could add the
>    following hook method to the DefaultFlushEntityEventListener class:
>      protected boolean requiresDirtyCheck(FlushEntityEvent event);
>    By default, this method would call EntityEntry#requiresDirtyCheck(Object entity)
>    as is done right now.
>    Resetting the dirty flag could maybe be done in Interceptor#postFlush() or some
>    dedicated method could be provided.
> BTW, I know that currently there already is the Interceptor#findDirty() method which
> already allows for some custom dirty checking but the problem from a performance
> point of view is that this method requires the entity's property values as parameter
> which are retrieved in DefaultFlushEntityEventListener#getValues() which is the most
> expensive method during flush. This drawback of the findDirty() method has often been
> noticed in comments on the news groups.
> I personally think it would be nice if something could be done to improve the
> performance of flushing in Hibernate since from what I read on the news groups and
> the like, flushing still seems to often lead to performance problems in practice,
> especially in larger projects where it is often not easy to avoid flushes or to
> keep the numer of entities in the session cache small. In fact, we are having quite
> some trouble with that in our project and having some custom dirty checking like the
> one I'm proposing here would greatly help in our project and in other projects as
> well, I guess.

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