[orm-devel] one2one relationship's behavior when reassigning (was: Bug or feature in relationships.py)

[Diedrich Vorberg]

Hi Mike!

>Line 172 of relationships.py in the set method of one2oneColumn contains:
>         if self._data: self._data.delete()

Mike's
> is a slightly different use case than what (I think) one2one 
>envisions. The example Diedrich uses is a photograph to a person. I guess I 
>can see deleting a photograph row if the persons photo is being replaced 
>with another, so the delete that happens in lock step with the status_id 
>attribute reassignment could make sense.

Orm thinks in objects. So a one2one relationship is a relationship
between objects. Deleting the parent also deletes the child as

   >>> del obj

also deletes obj's attributes... if obj is the only reference to 
them. 

>When a document has its status changed, the relationship between Document 
>and a row in Status should change, but no rows in Status should be deleted.

I can see that...

>one2one functionally delivers all that is needed with the important 
>exception of that delete happening on line 172. I guess I could just 
>subclass it and modify its behaviour for myself but I imagine I'm not the 
>only person with this need so here I am raising this.

and I too think subclassing is a good idea. It is a new kind of for orm
relation and should get a good name. From your eMail I guess 'lookup' 
suggests itself. At the company I used to work for these were 
referred to as 'domain tables", so perhaps 'domain' or 'domain_table'
would be a good idea. What do you think?

Diedrich

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