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

Diedrich Vorberg orm-devel@mailman.tux4web.de
Mon, 17 Feb 2003 23:44:43 +0100

Hi Mike!

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

> 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 

>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 Vorberg
         .'     '.
        /  _   _  \                         http://www.tux4web.de
        | (o)_(o) |                         info@tux4web.de
         \(     ) /            .---.
         //'._.'\ \           /     \       Internet Dienstleistungen
        //   .   \ \          \.@-@./       und 'Consulting'.
       ||   .     \ \         /`\_/`\
       |\   :     / |        //  _  \\      Linux Rules!
       \ `) '   (`  /_      | \     )|_
     _)``".____,.'"` (_    /`\_`>  <_/ \
     )     )'--'(     (    \__/'---'\__/
      '---`      `---`