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

[Emmanuel Bernard]

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

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 :)


On  Mar 4, 2009, at 14:38, Dan Allen wrote:

> On Wed, Mar 4, 2009 at 2:17 PM, Emmanuel Bernard <emmanuel at hibernate.org 
> > wrote:
> Then add @*to*(cascade=CascadeType.PERSIST), it will take you 2 mins  
> to do what you really like and you will know you do it.
>
> It doesn't take two minutes when you have 80 entities. Most apps  
> have large databases. Rarely do you see simple schemas like we have  
> in the examples. When you generate your entities again and have to  
> start all over. I think this is a good default to have, as well as  
> DELETE and maybe REFRESH. Daniel can speak better to what he is  
> seeing out in the field.
>
> NONE is a crappy default.
>
> -Dan
>
> -- 
> Dan Allen
> Senior Software Engineer, Red Hat | Author of Seam in Action
>
> http://mojavelinux.com
> http://mojavelinux.com/seaminaction
>
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