[Django]-Django admin: how to sort by one of the custom list_display fields that has no database field

by

188👍

✅

I loved Greg’s solution to this problem, but I’d like to point that you can do the same thing directly in the admin:

from django.db import models

class CustomerAdmin(admin.ModelAdmin):
    list_display = ('number_of_orders',)

    def get_queryset(self, request):
    # def queryset(self, request): # For Django <1.6
        qs = super(CustomerAdmin, self).get_queryset(request)
        # qs = super(CustomerAdmin, self).queryset(request) # For Django <1.6
        qs = qs.annotate(models.Count('order'))
        return qs

    def number_of_orders(self, obj):
        return obj.order__count
    number_of_orders.admin_order_field = 'order__count'

This way you only annotate inside the admin interface. Not with every query that you do.

👤bbrik

52👍

I haven’t tested this out (I’d be interested to know if it works) but what about defining a custom manager for Customer which includes the number of orders aggregated, and then setting admin_order_field to that aggregate, ie

from django.db import models 


class CustomerManager(models.Manager):
    def get_query_set(self):
        return super(CustomerManager, self).get_query_set().annotate(models.Count('order'))

class Customer(models.Model):
    foo = models.CharField[...]

    objects = CustomerManager()

    def number_of_orders(self):
        return u'%s' % Order.objects.filter(customer=self).count()
    number_of_orders.admin_order_field = 'order__count'

EDIT: I’ve just tested this idea and it works perfectly – no django admin subclassing required!

👤Greg

0👍

The only way I can think of is to denormalize the field. That is – create a real field that get’s updated to stay in sync with the fields it is derived from. I usually do this by overriding save on eith the model with the denormalized fields or the model it derives from:

# models.py
class Order(models.Model):
    bar = models.CharField[...]
    customer = models.ForeignKey(Customer)
    def save(self):
        super(Order, self).save()
        self.customer.number_of_orders = Order.objects.filter(customer=self.customer).count()
        self.customer.save()

class Customer(models.Model):
    foo = models.CharField[...]
    number_of_orders = models.IntegerField[...]
👤Andy Baker

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