Question

I have the following sample models:

class Note(models.Model):
    text = models.TextField()
    author = models.OneToOneField(User)
    date_created = models.DateField(auto_now_add=True)
    similar_note =  models.ForeignKey("self", related_name='similar_note', null=True, blank=True)

Say there are two notes Winner and Loser.

Loser has a field similar_note that points to Winner Note.

When I delete any of the two, both gets deleted, how do I prevent this from happening?
I have tried doing the same from the django admin interface as well, it happens from there as well.

PS: I am using django1.2, please don’t advice to upgrade, there are way too many constraints.

Answer 1

As mentioned here:

When Django deletes an object, by default it emulates the behavior of
the SQL constraint ON DELETE CASCADE — in other words, any objects
which had foreign keys pointing at the object to be deleted will be
deleted along with it.

This cascade behavior is customizable via the on_delete argument to
the ForeignKey

Please check the on_delete parameter for model field:

user = models.ForeignKey(User, blank=True, null=True, on_delete=models.SET_NULL)