Django migrations with foreign key

Question

I' trying to migrate this model:

class Questionpart_image(models.Model):
    questionpart = models.ForeignKey(Questionpart, null=True, blank=True)
    image = models.ImageField()

to this:

class Questionpart_image(Questionpart): # notice this base class
    image = models.ImageField()

to make advantage of inheritance. Django produces the following migration:

class Migration(migrations.Migration):

dependencies = [
    ('ochsite', '0016_auto_20150809_1903'),
]

operations = [
    migrations.RemoveField(
        model_name='questionpart_image',
        name='id',
    ),
    migrations.RemoveField(
        model_name='questionpart_image',
        name='questionpart',
    ),
    migrations.AddField(
        model_name='questionpart_image',
        name='questionpart_ptr',
        field=models.OneToOneField(default='', primary_key=True, to='ochsite.Questionpart', serialize=False, parent_link=True, auto_created=True),
        preserve_default=False,
    ),
]

but this does not set the right foreign key to questionpart_ptr from questionpart field. How can I achieve that?
I've been searching for a long time, but nothing...thanks

GwynBleidD · Accepted Answer · 2015-08-09 21:12:55Z

1

Simply don't rely on automatic migrations, make your own or modify that one.

Simplest solution will be by moving AddField in migration to the top of the list and inject between it and RemoveFields RunPython block that will rewrite id's from old field to new (and in other direction in reverse, if needed).

answered Aug 9, 2015 at 21:12

GwynBleidD

20.6k5 gold badges51 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

MartinM Over a year ago

Thank you, I ended up with creating completely new models, migrating data and deleting old models. It's a bit more complicated but it's safe.

Collectives™ on Stack Overflow

Django migrations with foreign key

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related