On Wed, May 13, 2009 at 7:22 PM, Carlos A. Carnero Delgado <
carloscarn...@gmail.com> wrote:
>
> Hello,
>
> I'm trying to get an aggregate to work. These are the (abridged) domain
> objects:
>
> class Site(models.Model):
> name = models.CharField(max_length=512)
>
> class Archive(models.Model):
> site = models.ForeignKey(Site)
> file_system_object = models.FileField(upload_to='.')
> downloads = models.PositiveIntegerField()
>
> That is, each "Site" can have any number of "Archive". I'd like to
> aggregate, and annotate, the total size of archives for each site.
>
> Just for the sake of testing, and to verify that the "plumbing"
> (relations) work, I can readily do
>
> Site.objects.annotate(downloads=Sum('archive__downloads'))
>
> and I'm getting what I expect. But I just hit a roadblock with the
> size, since it is an attribute of file_system_object.
>
> Can I aggregate over a field property?
>
> Best regards,
> Carlos.
>
> >
>
No, since the size isn't stored in the database you need to pull it into
Python to do those computations. If you denormalized the size of the file
as an additional field in the DB then you could aggregate over it.
Alex
--
"I disapprove of what you say, but I will defend to the death your right to
say it." --Voltaire
"The people's good is the highest law."--Cicero
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