[Answered ]-Django-notification: How many observed items

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1👍

✅

You can accomplish that by using annotations:

from django.db.models import Count
MyModel.objects.annotate(num_users=Count('watchers')).order_by('num_users')
👤Gonzalo

1👍

The problem is that django-notification uses generic foreign keys.

So I’ve redefined my watchers field:

watchers = generic.GenericRelation(notification.ObservedItem)

Then I can get all the watchers for a specific instance of MyModel.

$x = MyModel.objects.get(id=1)
$x.watchers.all()
$[<ObservedItem: ObservedItem object>, <ObservedItem: ObservedItem object>, <ObservedItem: ObservedItem object>]
$x.watchers.count()
$3

Close but no cigar. I wanted to do was something like this:

MyModel.objects.annotate(count=Count('watchers')).order_by('count')

Which is something that Django can’t do, according to the docs.

Django’s database aggregation API doesn’t work with a GenericRelation.

Not to worry, I think this will probably help:

http://charlesleifer.com/blog/generating-aggregate-data-across-generic-relations/

Repo is here:

https://github.com/coleifer/django-generic-aggregation

I’ve not tried it out yet…

👤powlo

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