Override UserManager in django

Question

How can I use a custom manager for the auth_user class in django?

In my django project, I'm using auth_user and I have a basic profile class. In every page of my site, I use some user and profile data, so every user query should join profile.

I wanted to use select_related in the get_query_set() method in a custom manager, but I cannot find any proper way to define one, or to override the existing UserManager. Any ideas?

Note: I don't want to override the user model. Or, to be more precise, I already overrode it in different proxy models. I want this custom manager to be used in every proxy model.

Answer 1

Ok, finally found the correct answer. The cleanest way is to use a custom authentication backend.

# in settings:
AUTHENTICATION_BACKENDS = ('accounts.backends.AuthenticationBackend',)


# in accounts/backends.py:
from django.contrib.auth.backends import ModelBackend
from django.contrib.auth.models import User


class AuthenticationBackend(ModelBackend):
    def get_user(self, user_id):
        try:
            # This is where the magic happens
            return User.objects. \
                select_related('profile'). \
                get(pk=user_id)
        except User.DoesNotExist:
            return None

Answer 2

This is fairly ugly but you can probably monkeypatch the User objects property, eg. in a middleware:

# manager.py
from django.contrib.auth.models import UserManager

class MyUserManager(UserManager):
    def get_query_set(self):
        qs = super(MyUserManager, self).get_query_set()
        return qs.select_related('profile')

---

# middleware.py
from django.contrib.auth.middleware import AuthenticationMiddleware
from managers import MyUserManager

class MyAuthMiddleware(AuthenticationMiddleware):
    def process_request(self, request):
        super(AuthenticationMiddleware, self).process_request(request)
        User.objects = MyUserManager()
        return None

Then replace the line in settings.py:

MIDDLEWARE_CLASSES = (
    # ...
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    # ...
)

By:

# settings.py
MIDDLEWARE_CLASSES = (
    # ...
    'yourapp.middleware.MyAuthMiddleware',
    # ...
)

Note1: This code is purely theoric, never tested nor I have the time to.

Note2: I couldn't recommend using this solution from a long-term maintenability point of view.

Note3: If someone suggest something else, you should probably listen to him or her more than me.

Note4: As a probably better idea, why not trying to query for Profile, which is a model class you have total control on? You can always retrieve the user object from a profile anyway, so…