id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
17863	Storing user and user profile in different databases?	Henning Kage <henning.kage@…>	nobody	"I am not sure, if this is a possible bug or a wanted feature. I want to outsource all tables from a Django application in a separate database. This includes the user profile, that I want to be stored in the app's own database. I am using the following minimal project, to reproduce the traceback:

'''settings.py'''

{{{
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3', 
        'NAME': 'default.db', 
    },
    'app': {
        'ENGINE': 'django.db.backends.sqlite3', 
        'NAME': 'app.db', 
    }
    
}
DATABASE_ROUTERS = ['app.router.Router']
INSTALLED_APPS = [
  # ...
  'app',
  ]
AUTH_PROFILE_MODULE = 'app.UserProfile'
}}}

'''app/models.py'''

{{{
#!python
from django.contrib.auth.models import User
from django.db import models

class UserProfile(models.Model):
    
    user = models.ForeignKey(User)
}}}

'''app/router.py'''

{{{
#!python
# -*- coding: utf-8 -*-

class Router(object):

    def db_for_read(self, model, **hints):
        if model._meta.app_label == 'app':
            return 'app'
        return None

    def db_for_write(self, model, **hints):
        if model._meta.app_label == 'app':
            return 'app'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        if (obj1._meta.app_label == 'app'
            or obj2._meta.app_label == 'app'):
            return True
        return None

    def allow_syncdb(self, db, model):
        if db == 'app':
            return model._meta.app_label == 'app'
        elif model._meta.app_label == 'app':
            return False
        return None
}}}

'''app/tests.py'''

{{{
#!python
from django.contrib.auth.models import User
from django.test import TestCase

from app.models import UserProfile

class SimpleTest(TestCase):

    def test_userprofile(self):
        u = User()
        u.save()
        p = UserProfile()
        p.user = u
        p.save()
        u.get_profile()
}}}

Although it is possible to specify a custom user profile class, Django always assumes, that the user profile model is saved in the same database Django stores the auth_user table. The unittest will result in the following traceback by calling the user's profile with `User.get_profile`:

{{{
Traceback (most recent call last):
  File ""/Users/henningkage/Projekte/sandbox/userprofile/app/tests.py"", line 14, in test_userprofile
    u.get_profile()
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/contrib/auth/models.py"", line 401, in get_profile
    self._state.db).get(user__id__exact=self.id)
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/models/query.py"", line 361, in get
    num = len(clone)
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/models/query.py"", line 85, in __len__
    self._result_cache = list(self.iterator())
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/models/query.py"", line 291, in iterator
    for row in compiler.results_iter():
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/models/sql/compiler.py"", line 763, in results_iter
    for rows in self.execute_sql(MULTI):
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/models/sql/compiler.py"", line 818, in execute_sql
    cursor.execute(sql, params)
  File ""/Users/henningkage/Python/django_multi_db/src/django/django/db/backends/sqlite3/base.py"", line 337, in execute
    return Database.Cursor.execute(self, query, params)
DatabaseError: no such table: app_userprofile
}}}

Does Django needs the user and user profile model in the same database as foreign keys across multiple databases are not possible? My attached (minmal) change will return a valid user profile model instance. The only disadvantage to me is the fact, that the user profile has no real relation to the user and will only return the user's id. This would be the normal behaviour for relationships across multiple databases. But it would be possible to store the user profile in a different database than Django's internal tables. If this topic has already been discussed and I missed it, sorry for the ticket."	Bug	closed	contrib.auth	dev	Normal	wontfix			Unreviewed	1	0	0	0	0	0