How To Migrate to a Custom User Model

If you are using the built-in Django User model and you want to switch to an authtools-based User model, there are certain steps you have to take in order to keep all of your data. These are steps that have worked for me in the past, maybe they will help to inform your journey.

This tutorial assumes that you already have users in your database and that you need to preserve that data. If you don’t already have users in your database, you can switch easily already.

Step 1: Backup your database

There are several commands for doing this depending on your RDBMS (pg_dump, mysqldump, cp). If you don’t want to worry about those, you could also look for a solution like django-backupdb. You do not want to start this process without having a backup of your database.

Step 2: Make a new app

This is the app where your custom User model will live. I usually call this app accounts.

$ python manage.py startapp accounts

In your new app, edit the models file and add the following:

from django.db import models
from django.contrib.auth.models import AbstractUser

class User(AbstractUser):
    class Meta:
        db_table = 'auth_user'

This will put the User model in the same database table as the old one. This is not ideal, but it is the easiest way to do this migration.

Add your accounts app to INSTALLED_APPS.

Set the AUTH_USER_MODEL setting to point to your new User model.

AUTH_USER_MODEL = 'accounts.User'

If your code has any references to Django’s User model, you will have to go through and replace them with generic references. In most places, this means using get_user_model() instead of User. For models with a database relationship to User, you should use settings.AUTH_USER_MODEL.

Step 3: Seize control

Generate an initial migration for the accounts app.

$ python manage.py makemigrations accounts

If you are working on a new database and are running the migrations from scratch, you can run that migration normally. However, if you are working on an existing database, this migration will fail because the tables it attempts to create already exist. In this type of situation, the solution would usually be to fake apply the migration, but doing so in this case will cause Django to raise an InconsistentMigrationHistory exception. There a couple of ways around this.

One solution would be to delete all your old migration files, truncate the migrations table in the database, create new migrations, and then fake apply them as outlined in this tutorial.

This is not ideal. Instead, I suggest another solution that preserves your migration history. Thanks to this blog post by Tobias McNulty for the idea.

Start by opening up a database shell.

$ python manage.py dbshell

Then manually add the migration to the database like this:

INSERT INTO django_migrations (app, name, applied) VALUES ('accounts', '0001_initial', CURRENT_TIMESTAMP);

Finally, update the django_content_type table with the new app_label so that existing references will point to your new user model. You can then exit the shell.

UPDATE django_content_type SET app_label = 'accounts' WHERE app_label = 'auth' and model = 'user';

Warning

Make sure to test this process in a staging environment. If your deployment process automatically runs migrate, you will need to run the 2 SQL statements above beforehand or the migration command will fail.

Step 4: Conquer

Your accounts app is now the authoritative source for the User model. You are in charge now.

Go build stuff.

Optional Step 5: Customize

Warning

There is a potential unique constraint failure here. If you don’t have emails for all of your users, you won’t be able to migrate. If you don’t have emails for all of your users, they won’t be able to log in either, so you should make sure that you have all of those email addresses first.

Now that you have control of the User model, there are tons of customizations that you can do. One thing that I like to do is treat email as the username and get rid of first_name/last_name in favor of a single name field. Here’s how I’ve done it in the past.

1. Install django-authtools.

   $ pip install django-authtools
   

2. Add authtools to your INSTALLED_APPS.

   INSTALLED_APPS = (
       ...
       'authtools',
       ...
   )
   

3. Add the fields that I want to User. In this case, all I want to add is name. email already exists on User, but I do need to make it unique if I’m going to treat it as a username.

   Here is an implementation of the User model using authtools.models.AbstractNamedUser as a base. It preserves all of the fields that are on the built-in User model, but adds name and treats email as the username.

   from django.db import models
   from django.utils.translation import gettext_lazy as _
   
   from authtools.models import AbstractNamedUser
   
   
   class User(AbstractNamedUser):
       username = models.CharField(_('username'), max_length=30, unique=True)
       first_name = models.CharField(_('first name'), max_length=30, blank=True)
       last_name = models.CharField(_('last name'), max_length=30, blank=True)
   
       class Meta:
           db_table = 'auth_user'
   

   I still have first_name and last_name because I have to preserve that data, I will get rid of those fields in step 5.

4. Make a migration to add those fields.

   $ python manage.py makemigrations accounts
   

5. Add python functions to run with the migration that consolidate first_name/last_name into name (and vice-versa when rolling-back).

   def forwards(apps, schema_editor):
       User = apps.get_model('accounts', 'User')
       for user in User.objects.all():
           user.name = user.first_name + ' ' + user.last_name
           user.save()
   
   def backwards(apps, schema_editor):
       User = apps.get_model('accounts', 'User')
       for user in User.objects.all():
           user.first_name, _, user.last_name = user.name.partition(' ')
           user.save()
   

   Add these functions to the list of operations in the generated migration file.

   operations = [
       ...,
       migrations.RunPython(forwards, backwards),
   ]
   

   The backwards migration does make some assumptions about how names work, but those are the assumptions you are forced to make when using a system that assumes people have two names.

6. Delete the columns you don’t want on your User model. For me, that’s username, first_name, and last_name. My User model now looks like this:

   class User(AbstractNamedUser):
       class Meta:
           db_table = 'auth_user'
   

7. Generate a migration that deletes those extra fields.

   $ python manage.py makemigrations accounts
   

8. Run the migrations.

   $ python manage.py migrate accounts
   

9. Watch YouTube. You are done.