[seam-dev] To cascade or not...

[Dan Allen]

On Wed, Mar 4, 2009 at 2:59 PM, Emmanuel Bernard <emmanuel at hibernate.org>wrote:

> class Address {  @ManyToOne Country country;
>   @ManyToOne State state;
>   @ManyToMany Set<Person> inhabitants;
> }
>
> It generally makes no sense to cascade persist for these three
> associations. Even if your app has 80 entities, it's very likely that half
> of the associations should not be cascaded :)
>
> Let's take your proposal
> PERSIST, DELETE, REFRESH
>
> I REFRESH address and changes on Person are lost, doh!
>

True. I was on the fence about REFRESH. I think you convinced me.


> PERSIST, do I really save an address and expect the person living there to
> be added to the system. Surely not, the person is very likely to have been
> built beforehand. Same for Country and State.
>

Not a problem if County and State are managed, which is likely how you
attach them anyway. It will even work if they are a non-managed entity with
a valid ID. If neither of those are the case, then yes, I want the persist
to add them to the database. That's the whole point of the cascade.


> MERGE Do I really want to update a country when an address changes? I can't
> find a system that would do that.
>

I don't do MERGE, so I don't care.


> Cascade has performance consequences. The more cascades the slower your app
> will be at flush time. Especially on applications with a lot of entities.
>
> NONE is a good default, that's why it's the default we have chosen :)
>

I'm still don't agree. I like PERSIST and DELETE. DELETE can be dangerous,
but it's also extremely convenient.

-Dan

-- 
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action

http://mojavelinux.com
http://mojavelinux.com/seaminaction

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