Hi Ramsey, On 10/11/2011, at 4:24 AM, Ramsey Gurley wrote:
> On Nov 8, 2011, at 8:34 PM, Paul Hoadley wrote: > >> So the advice is that the intended delete rule(s) should operate on the real >> relationship chain, not shortcut via the flattened relationship. That's >> fine, but are Nullify and Do Nothing really interchangeable on a flattened >> relationship, as it's almost suggested above? It's important because the >> default is Nullify, so all flattened relationships have that rule unless you >> change them. But depending on whether that rule is applied before or after >> the rule(s) applied over the real relationship chain, Nullify might end up >> giving you the wrong semantics. Shouldn't all flattened relationships have >> a Do Nothing delete rule (at least by default)? > Not all... at least not flattened many to many. Those cascade. Which led me > to a surprising find as well. The opposite side of that cascade is nullify, > which I thought was incompatible with cascade. But, evidently, it works and > I can see why it would be needed on the other side of the delete. Say I have two entities, User and Role, and a joining entity UserRole to create a many-to-many relationship between them. So I have a relationship 'userRoles' from User to UserRole (and a relationship 'userRoles' from Role back to UserRole). I flatten the relationship on User, so I also have a 'roles' relationship on that entity. Say I delete a User. I want User.userRoles to Cascade. And I want both UserRole.user and UserRole.role to Nullify. And at that point, isn't the work done? So in this case, wouldn't I want No Action on User.roles? And hence isn't this a counter-example to your advice above? (It may well not be—tell me if I'm wrong!) -- Paul. http://logicsquad.net/ _______________________________________________ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
