Django - How to get only 2 object for a combination of fields with a queryset

Question

If I have

Model.objects.all()

I want to get only one object for any content_object=foo, object_id=N. How can I do that? Say I am ordering by -datetime. If I can get only one object in the queryset for any content_type=foo, object_id=N ... it should be the latest.. How to specify that I only want 1 object for any combination of content_object and object_id?

class CheckIn(models.Model):
    ...
    owner = models.ForeignKey('auth.User')
    datetime = models.DateTimeField(editable=False, auto_now=True)

    ...
    # This is the object that should be geocoded, hopefully
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey()

    class Meta:
        ordering=( '-datetime', )

Then to take a queryset:

checkins = CheckIn.objects.filter(
        datetime__gte=datetime.datetime.now() -
        datetime.timedelta(hours=24),
)

this can give me all of the checkins within the last 24 hours but I only want 1 object PER content_type=foo and object_id=N.

Answer 1

Do you want to find latest Model object after some filtering? What do you mean by object id ? Is it a foreign key? Or it is the Model id auto generated by django? I guess it is the later. In that case, you can use just id. This may help you (I am assuming that you have at least these fields in your Model: content_object, dateField ):

Model.objects.filter(content_object=foo,id=N).order_by(dateField)[0]

EDIT:

I apologize. Well, the question was not this clear at the beginning (and I am a newb). Here is a naive approach (I think you want distinct):

d={}
[d.setdefault(str(a.content_type)+str(a.object_id),a) for a in checkins ]
d.values() # this gives your desired list of distinct objects