User != UserEmail
User does not have subject, thus it will raise AttributeError: 'User'
object has no attribute 'subject'
Secondly, I do not want to create 1+N queries (where N is number of
users), with creating a query per user this would be simple but very
inefficient.
On Jan 16, 12:16 pm, Praveen Krishna R <rpraveenkris...@gmail.com>
wrote:
> *First of all did you try accessing the email subject with a dotted
> notation?*
> try
> u = User.objects.all()
> and
> u[0].subject
>
> On Sun, Jan 16, 2011 at 12:53 PM, Jari Pennanen
> <jari.penna...@gmail.com>wrote:
>
>
>
>
>
>
>
>
>
> > Hi!
>
> > Suppose following model:
>
> > class UserEmail(models.Model):
> > """User email"""
>
> > user = models.ForeignKey(User, db_index=True,
> > null=True, blank=True, editable=False)
> > """User recieving the email"""
>
> > added = models.DateTimeField(_("added"), auto_now_add=True)
> > """Added to database"""
>
> > subject = models.CharField(_('subject'), max_length=128)
> > """Subject"""
>
> > message = models.TextField(_('message'))
> > """Message"""
>
> > How can I retrieve list of users and their latest email subject?
>
> > This almost works:
>
> > User.objects.all()\
> > .annotate(latest_email_added=Max('useremail__added'))
>
> > But it does not give me the other fields of latest email such as
> > subject, so I try to add other fields using extra:
> > User.objects.all()\
> > .annotate(latest_email_added=Max('useremail__added'))\
> > .extra(select={'email_subject' : 'myapp_useremail.subject'})
>
> > Suddenly it adds a GROUP BY to the query with a long list of fields
> > that should not be there, which breaks everything, now I get multiple
> > rows per user which is not wanted.
>
> > If I try to modify the group_by manually, like this:
> > a = User.objects.all()\
> > .annotate(latest_email_added=Max('useremail__added'))\
> > .extra(select={'email_subject' : 'dmusic_useremail.subject'});
> > a.query.group_by = [('auth_user', 'id')];
> > print a.query
>
> > There is still one extra field in group by making it break:
> > ... GROUP BY "auth_user"."id", (dmusic_useremail.subject)
>
> > Can someone elaborate this behavior?
>
> > Any help is appreciated, thanks!
>
> > --
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> > .
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>
> --
> *Praveen Krishna R*
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