On Fri, 2008-09-26 at 16:29 +0200, Alessandro wrote:
> I have a model with a m2m field "provincia".
> I want to order my objects in this way:
> If the object has a provincia = 'AA' on m2m relation must be the
> bottom of my list.
>
> I tried query = query.order_by('-provincia') and it works correctly
> (because AA is the first of the values), but I duplicates the results
> because of multiple m2m relationships:
> If an object has both "FC" and "BO" in provincia, I will have 2
> objects in queryset also If I use distinct().
That's correct, since the fields you are ordering on are part of the
selected columns, so they make the entries non-distinct.
>
> Is there a solution?
Not really, except for writing a raw SQL query. The raw SQL for this
type of query is very complicated and it's such an edge case (it's
trying to do if-then logic in SQL when you write it out) and not always
even possible, so Django doesn't even try. If you order on a
multi-valued field and have more than one related value, you'll get
multiple rows.
You might want to prefer to do the ordering in Python or as a second
pass. Or you could try to write the raw SQL, but it could be fairly
messy.
Regards,
Malcolm
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