Question

I’m starting a new project and plan on using nhibernate. I’m struggling with whether or not I should keep my domain model clean of persistence information by leaving out foreign keys. I keep feeling like some of my ‘model’ isn’t really necessary and that performance is going to be an issue. For example:

In my db I have the following table:

Posting     Id     StatusId     ... 

Which has an FK relationship with this table:

PostingStatus     Id     Name 

In my model I’ve defined 2 classes:

class Posting {     virtual int Id { get; set; }     virtual PostingStatus Status { get; set; }     // .. }  class PostingStatus {     virtual int Id { get; set; }     virtual string Name { get; set; } } 

Does PostingStatus belong in my model? and in cases where I know the FK ahead of time, like updating a posting after a submit, isn’t it a pretty heavy performance hit (or just useless work) to have nhibernate fetch a PostingStatus instance instead of just setting a FK?

I’m pretty sure this issue has been discussed before but I keep finding bits an pieces of the discussion that have shotty relevance. Thoughts or resources on this issue would be greatly appreciated.

Answer 1

If the Domain Model requires relationships to be enforced then you need Foreign Keys.

Don’t worry about performance until you actually have a performance problem.