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 are using South for migrations. If you aren’t you probably should be using it. Unless of course, it’s the future and the schema-alteration of Django has been completed and merged.

It also 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 switch easily already.

This tutorial shows the easy way to migrate custom Users, keeping the same database table. If you want to move to your own database table, there is an excellent answer on StackOverflow.

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.

Steps 2 and 3 are actually completely safe. They don’t actually affect the database. What they do accomplish is moving the authoritative source of control over the User model class from django to your code.

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'

Step 3: Seize control

Generate an initial migration for the accounts app.

$ python manage.py schemamigration --initial 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. You will have to fake run this migration.

$ python manage.py migrate --fake accounts 0001

Note

If you are very certain that these migrations will never be run on an empty database, you can replace the bodies forwards and backwards migrations with pass. This is not a good idea though.

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 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 ugettext_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. When you are altering the schema and migrating data, the South tutorial on data migrations recommends that you split it up into 3 steps.

3. Make a schema migration to add those fields.

   $ python manage.py schemamigration --auto accounts
   

4. Make a data migration to copy first_name/last_name into name.

   $ python manage.py datamigration accounts consolidate_name_field
   

   Here is an example of a migration that does this:

   class Migration(DataMigration):
       def forwards(self, orm):
           for user in orm['accounts.User'].objects.all():
               user.name = user.first_name + ' ' + user.last_name
               user.save()
   
       def backwards(self, orm):
           for user in orm['accounts.User'].objects.all():
               # If there are more than two names, assume that the rest
               # are their last names.
               user.first_name, _, user.last_name = user.name.partition(' ')
               user.save()
   

   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.

5. 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'
   

6. Generate a migration that deletes those extra fields.

   $ python manage.py schemamigration --auto accounts
   

   You will be presented with a question about what to do in the backwards migration. The username field was non-nullable, which means it’s impossible to go back. I would select to disable backwards migrations.

7. Run the migrations.

   $ python manage.py migrate accounts
   

8. Watch YouTube. You are done.