Auto Incremement when id=0 in dict is passed to save()

Using Django Using the ORM
1 
from .models import DummyModel
dict = {'id': 0, 'fieldA': 'value-1', 'fieldB': 'value-2', 'fieldC': 'value-3', 'active_flag': 0, 'date': '2024-03-11'}
dummy = DummyModel(**dict)
dummy.save()

ValueError: The database backend does not accept 0 as a value for AutoField.

I thought that if id is 0 it’ll automatically do a auto increment ?

2

Hey there!
If you primary key field is auto-generated (in this case the id field) then you should not initialize the model with a value if you want it to be auto-generated.
This happens because django uses the same method to create/update (save method), so after a auto-generated field has a value populated, it won’t generate a new one. Otherwise instead of updating a row, it would be creating a new one every-time.

If you have control over the dict creation/initialization you can omit the id field of the keys.
If you don’t have control over the dict creation/initialization you can remove that key if the value is 0.

3

So I’ve edited my code to as follows :

_id = int(d.get("id", "0"))
dict['id'] = _id
fields = list(dict.keys())

if _id > 0:
    fields.remove('id')
    dummy = DummyModel(**dict)
    dummy.save(force_update=True, update_fields=list(fields))
else:
    del dict['id']
    dummy = DummyModel(**dict)
    dummy.save()

_id = dummy.id
4

Is there any particular reason for you not to query the DummyModel object from the database? This seems a bit “exotic” way of updating the object, skipping validation and shooting yourself on the foot.

5

Im using the same code for insert and update. The form UI is the same for both.