Django ForeignKey which does not require referential integrity?

I'm new to Django, so I don't now if it provides what you want out-of-the-box. I thought of something like this:

from django.db import models

class YourModel(models.Model):
    my_fk = models.PositiveIntegerField()

    def set_fk_obj(self, obj):
        my_fk = obj.id

    def get_fk_obj(self):
        if my_fk == None:
            return None
        try:
            obj = YourFkModel.objects.get(pk = self.my_fk)
            return obj
        except YourFkModel.DoesNotExist:
            return None

I don't know if you use the contrib admin app. Using PositiveIntegerField instead of ForeignKey the field would be rendered with a text field on the admin site.

To do the solution by @Glenn Maynard via South, generate an empty South migration:

python manage.py schemamigration myapp name_of_migration --empty

Edit the migration file then run it:

def forwards(self, orm):
    db.delete_foreign_key('table_name', 'field_name')

def backwards(self, orm):
    sql = db.foreign_key_sql('table_name', 'field_name', 'foreign_table_name', 'foreign_field_name')
    db.execute(sql)

Source article

This is probably as simple as declaring a ForeignKey and creating the column without actually declaring it as a FOREIGN KEY. That way, you'll get o.obj_id, o.obj will work if the object exists, and--I think--raise an exception if you try to load an object that doesn't actually exist (probably DoesNotExist).

However, I don't think there's any way to make syncdb do this for you. I found syncdb to be limiting to the point of being useless, so I bypass it entirely and create the schema with my own code. You can use syncdb to create the database, then alter the table directly, eg. ALTER TABLE tablename DROP CONSTRAINT fk_constraint_name.

You also inherently lose ON DELETE CASCADE and all referential integrity checking, of course.

This question was asked a long time ago, but for newcomers there is now a built in way to handle this by setting db_constraint=False on your ForeignKey:

https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey.db_constraint

customer = models.ForeignKey('Customer', db_constraint=False)

or if you want to to be nullable as well as not enforcing referential integrity:

customer = models.ForeignKey('Customer', null=True, blank=True, db_constraint=False) 

We use this in cases where we cannot guarantee that the relations will get created in the right order.

EDIT: update link