Does not automatically assign ID?

[Joakim Hove]

Disclaimers:

1. This issue is also on StackOverflow: https://stackoverflow.com/questions/64320386/django-postgresql-model-with-only-foreign-keys
2. I posted this here in this group a couple of days ago without finding a solution.

I must admit I am quite baffled by this problem, seems like a thing I have done for years suddenly does not work any longer?? In particular the code in question here has worked for a couple of months, and then "suddenly" stopped working - probably due to "apt get upgrade", but I can not pinpoint exactly when it stopped working. I post it again here with some corrections and a bit more detail. Hopefully someone can see what I do wrong; if someone wants to contact me off-list and offer commercial help I could be interested in that.

I have a model which looks like this:

class InputTypeMap(models.Model):
    input_type = models.ForeignKey(InputType, on_delete=models.CASCADE)
    training = models.ForeignKey(Training, on_delete=models.CASCADE)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    gender = models.ForeignKey(Gender, on_delete=models.CASCADE)

I.e. there are four fields in the model which are all foreign keys to other models. The primary key is not added explicitly by me, rather I trust Django to add the required primary key with an "invisible" AutoField. When I create a new instance of this class like:

InputTypeMap.objects.create(input_type=input_type,
                            training=training,
                            gender=gender,
                            category=category)

I get an exception:

Traceback (most recent call last):
  File "/home/hove/sleipner/venv/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.NotNullViolation: null value in column "id" violates not-null constraint
DETAIL:  Failing row contains (null, Maintenance, Female, MareGielding, No).

From the error message it seems to me that a ID key for the new entry is not generated; I was expecting postgres to do that itself? When the same code is run as a test on sqlite it works as intended.

Information about Postgres versions: Server 9.6 - Client 13

Joakim