Django migration strategy for renaming a model and relationship fields

At first, I thought that Fiver's method worked for me because the migration worked well until step 4. However, the implicit changes 'ForeignKeyField(Foo)' into 'ForeignKeyField(Bar)' was not related in any migrations. This is why migration failed when I wanted to rename relationship fields (step 5-8). This might be due to the fact that my 'AnotherModel' and 'YetAnotherModel' are dispatched in other apps in my case.

So I managed to rename my models and relationship fields doing following below steps:

I adapted the method from this and particularly the trick of otranzer.

So like Fiver let's say we have in myapp:

class Foo(models.Model):
    name = models.CharField(unique=True, max_length=32)
    description = models.TextField(null=True, blank=True)

And in myotherapp:

class AnotherModel(models.Model):
    foo = models.ForeignKey(Foo)
    is_awesome = models.BooleanField()


class YetAnotherModel(models.Model):
    foo = models.ForeignKey(Foo)
    is_ridonkulous = models.BooleanField()

Step 1:

Transform every OneToOneField(Foo) or ForeignKeyField(Foo) into IntegerField(). (This will keep the id of related Foo object as value of the integerfield).

class AnotherModel(models.Model):
    foo = models.IntegerField()
    is_awesome = models.BooleanField()

class YetAnotherModel(models.Model):
    foo = models.IntegerField()
    is_ridonkulous = models.BooleanField()

Then

python manage.py makemigrations

python manage.py migrate

Step 2: (Like step 2-4 from Fiver)

Change the model name

class Bar(models.Model):  # <-- changed model name
    name = models.CharField(unique=True, max_length=32)
    description = models.TextField(null=True, blank=True)

Create an empty migration:

python manage.py makemigrations --empty myapp

Then edit it like:

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0001_initial'),
    ]

    operations = [
        migrations.RenameModel('Foo', 'Bar')
    ]

Eventually

python manage.py migrate

Step 3:

Transform Back your IntegerField() into their previous ForeignKeyField or OneToOneField but with the new Bar Model. (The previous integerfield was storing the id, so django understand that and reestablish the connection, which is cool.)

class AnotherModel(models.Model):
    foo = models.ForeignKey(Bar)
    is_awesome = models.BooleanField()

class YetAnotherModel(models.Model):
    foo = models.ForeignKey(Bar)
    is_ridonkulous = models.BooleanField()

Then do:

python manage.py makemigrations 

Very importantly, at this step you have to modify every new migrations and add the dependency on the RenameModel Foo-> Bar migrations. So if both AnotherModel and YetAnotherModel are in myotherapp the created migration in myotherapp must look like this:

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '00XX_the_migration_of_myapp_with_renamemodel_foo_bar'),
        ('myotherapp', '00xx_the_migration_of_myotherapp_with_integerfield'),
    ]

    operations = [
        migrations.AlterField(
            model_name='anothermodel',
            name='foo',
            field=models.ForeignKey(to='myapp.Bar'),
        ),
        migrations.AlterField(
            model_name='yetanothermodel',
            name='foo',
            field=models.ForeignKey(to='myapp.Bar')
        ),
    ]

Then

python manage.py migrate

Step 4:

Eventually you can rename your fields

class AnotherModel(models.Model):
    bar = models.ForeignKey(Bar) <------- Renamed fields
    is_awesome = models.BooleanField()


class YetAnotherModel(models.Model):
    bar = models.ForeignKey(Bar) <------- Renamed fields
    is_ridonkulous = models.BooleanField()

and then do automatic renaming

python manage.py makemigrations

(django should ask you if you actually renamed the modelname, say yes)

python manage.py migrate

And that's it!

This works on Django1.8

So when I tried this, it seems you can condense Step 3 - 7:

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0001_initial'), 
    ]

    operations = [
        migrations.RenameModel('Foo', 'Bar'),
        migrations.RenameField('AnotherModel', 'foo', 'bar'),
        migrations.RenameField('YetAnotherModel', 'foo', 'bar')
    ]

You may get some errors if you don't update the names where it's imported e.g. admin.py and even older migration files (!).

Update: As ceasaro mentions, newer versions of Django are usually able to detect and ask if a model is renamed. So try manage.py makemigrations first and then check the migration file.

In the current version of Django you can rename the model and run python manage.py makemigrations, django will then ask if you want to rename the model and if you select yes, then all renaming process will be done automatically.