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From Jörg von Frantzius <joerg.von.frantz...@artnology.com>
Subject Re: Behavior of deletePersistent with datastore constraints
Date Wed, 12 Jul 2006 17:37:29 GMT
Hello Craig,

please see my comments below...

Craig L Russell schrieb:

[..]
> I'd like to discuss the two items above. The spec requires that 
> deletes be deferred until flush, but I suspect that this 
> overconstrains the possible implementations. I would leave it up to 
> the implementation to decide whether to delete immediately or defer 
> until flush. 
>
> But if it deletes the instance immediately, it would also have to 
> nullify any foreign keys that refer to it in order to avoid an 
> immediate constraint violation. And I don't believe that this should 
> be done automatically unless the user specifically asked for it, via a 
> metadata annotation on the
Why would we like to avoid immedate constraint violations in the first 
place? They only constrain the user in that that he/she has to remove 
objects from any associations before being able to delete them, and not 
afterwards. Alternatively, if the user finds that uncomfortable, he 
could make those FKs deferrable (if the DB allows it).
> foreign key delete-action=NULL. If the implementation wanted to 
> nullify the referring key where the constraint was defined as anything 
> else, it would have to guarantee at flush time that the user had set 
> the field to null or something else, or all the referring objects 
> themselves were deleted.
That sounds really very complicated. I'd wonder why someone would take 
on the effort only to mimic real deferred constraints (for the case of 
deletion only).
>
> With regard to integrity constraints, the second paragraph leaves me 
> cold. I don't know what I was thinking when I wrote "or the delete 
> operation is simply ignored". When would ignoring a delete from the 
> application ever be the right behavior?
That's what I had been wondering as well!

Regards,
Jörg
>
> Comments?
>
> Craig Russell
>
> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
>
> 408 276-5638 mailto:Craig.Russell@sun.com
>
> P.S. A good JDO? O, Gasp!
>
>


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