How to order a django query after a distinct operation

Question

I have the following code:

# Gets the most recent post from each user
# However, the returned set is not ordered by created_on
queryset = Post.objects.all().order_by('author', '-created_on').distinct('author')

Trying to, for example, tack another order_by onto the end of the query, or changing the current order_by parameters, results in this error: SELECT DISTINCT ON expressions must match initial ORDER BY expressions

Is there a way to accomplish my goal here (a list of each user's most recent post, ordered from newest to oldest)?

Answer 1

You don't, you will need to order it already before the .distinct(…) call ^[Django-doc] call.

You can for a class-based view override the .get_queryset() method ^[Django-doc] , and there construct the correct query, like:

from django.views.generic import ListView


class MyListView(ListView):
    # …
    def get_queryset(self):
        if something:
            return Post.objects.order_by('author', 'title').distinct('author')
        return Post.objects.order_by('author', '-created_on').distinct('author')