On Fri, 2009-04-10 at 02:05 -0700, chris wrote:
> Hi there,
>
> Here I am trying to use the aggregate functions available in SVN trunk
> (I am not sure if they have been released). The following is a
> simplified version of the models involved:
>
> class Edition(models.Model):
> edkey = models.TextField()
>
> class TextChar(models.Model):
> edition = models.ForeignKey(Edition)
> char= models.TextField(blank=True)
> unichar = models.ForeignKey(Char)
>
> class Char(AdminMetadata):
> unicode = models.CharField(max_length=7, blank=True)
>
> and here is what I am trying to do with them:
>
> In [55]: c = Char.objects.get(pk=1)
> In [56]: c.textchar_set.values('edition').annotate(Count('char'))
> Out[56]: [{'char__count': 46, 'edition': 1}, {'char__count': 1,
> 'edition': 2}]
>
> So I want to find out how many characters do occur in which edition
> and I get the result as expected. However, instead of the edition
> objects, what I get back are the pk values of the edition. Is there a
> way to change this so that I get the objects that can be rendered in a
> template?
The problem here is that there is no canonical object to give back. It's
an ambiguous request. You are asking for a char__count value per edition
value, not per TextChar object.
However there could be, and likely are, many TextChar objects with the
same edition value, so it would be ambiguous as to which particular
object to return. Since there's no natural choice, there's no API to ask
Django to guess or provide a sample object or anything like that. It's
not appropriate to return a model object for that type of query.
What is the real problem you are trying to solve here? Why do you need
an object back?
Regards,
Malcolm
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