force_insert doesn't work with inherited models

[Nicolas Dietrich]

The following testcase describes the problem best:

Model:

from django.db import models

class Parent(models.Model):
    something = models.SlugField()

class Daughter(Parent):
    pass

Interactive session:

In [1]: from appname.models import Daughter
In [2]: d = Daughter(something='algo')
In [3]: d.save()
In [4]: d.something='otra'
In [5]: d.save(force_insert=True)

results in

IntegrityError: duplicate key value violates unique constraint "appname_daughter_pkey"

[Malcolm Tredinnick]

That's not a bug, it's exactly the right behaviour. You created d and then you try to save it with updated data (the primary key will still be the same), but say you want to force an insert. The database says the record already exists with that primary key value.