Question

Suppose I have a Book model containing a foreign key to a Publisher model.

How can I display in the Django admin a column with the number of books published by each publisher, in a way that I can use the built-in sorting?

Answer 1

I had the same issue (I cannot change my model’s manager to add slow annotations or joins). A combination of two of the answers here works. @Andre is really close, the Django Admin supports modifying the queryset for just the admin, so apply the same logic here and then user the admin_order_field attribute. You still need to add the new admin field to list_display, of course.

from django.db.models import Count

class EventAdmin(admin.ModelAdmin)
    list_display = (..., 'show_artist_count')

    def queryset(self, request):
    # def get_queryset(self, request):    for Django 1.6+
        qs = super(EventAdmin, self).queryset(request)
        return qs.annotate(artist_count=Count('artists'))

    def show_artist_count(self, inst):
        return inst.artist_count
    show_artist_count.admin_order_field = 'artist_count'