Example of data migration for add/remove multi-table inheritance

datamigration.py

class Migration(DataMigration):
    def forwards(self, orm):
        """Based on solution:
            http://stackoverflow.com/questions/4064808/django-model-inheritance-create-sub-instance-of-existing-instance-downcast
        """
        parent_articles = orm['app.Parent'].objects.all()
        for article in parent_articles:
            children_article = orm['app.Children(parent_ptr=article)
            children_article.__dict__.update(article.__dict__)
            children_article.save()

    def backwards(self, orm):
        """Based on solution:
            http://stackoverflow.com/questions/3711191/django-deleting-object-keeping-parent
        """
        children_articles = orm['app.Children'].objects.all()
        attrs = {
            'title': 'Primeiro texto',
        }
        for article in children_articles:
            dummy = orm['app.Parent'].objects.create(**attrs)
            article.parent_ptr = dummy
            article.save()
            article.delete()

models.py

class Parent(models.Model):
    title = models.CharField(max_length=128)


class Children(Parent):
    subtitle = models.CharField(max_length=128)