Ordering a django queryset by sum of two (or more) fields

Question

I have found a few questions that are similar to mine, but most of them are dated, or too (or too little) verbose to be helpful.

I have a model like this:

class Breakfast(models.Model):
    count_eggs = models.IntegerField()
    count_bacon = models.IntegerField()
    had_toast = models.BooleanField()

Now, in building a RESTful API, I need the ability to sort Breakfast objects by the total of count_eggs + count_bacon without storing this permanently on the model.

Many of the current and popular questions suggest something like this:

Breakfast.objects.extra(
    select={'total_food':'count_eggs + count_bacon'},
    order_by=('total_food',)
)

This seems to work for many, but Django docs appear to dissuade this solution. So, in the 1.10+ world, What is the best/correct way to do this type of filtering on the sum of two (or more) fields in Django

Answer 1

You should use annotate, I got an example of mine and adapted to your case, try this:

from django.db.models import F, Sum

Breakfast.objects.all().\
            annotate(total_food=Sum(
                F('count_eggs ') + F('count_bacon'))
            ).\
            order_by('total_food')