ForeignKey cast to int despite being varchar

[fiomtec@…]

Hi!

I have a couple of models connected to a read-only sqlserver DB, like this (trimmed to the important details):

class Cliente(models.Model):
    codigo = models.CharField(max_length=8, primary_key=True)
    nif = models.CharField(max_length=15)
    nombre = models.CharField(max_length=100, db_column='nombre_apellidos')


class Confirmacion(models.Model):
    cliente = models.ForeignKey(Cliente, db_column='entidad_propietaria', max_length=8)
    [...]other fields[...]

When I try to find some Confirmacion objects filtering by nif like this:

Confirmacion.objects.filter(cliente__nif=nif).all()

it will correctly find some results, but blow up when I try to access them. e.g., this is a dict from one Confirmacion result:

{'cliente_id': 7502, '_state': <django.db.models.base.ModelState object at 0x000000000433C940>, [...] other fields [...]}

the problem is that the correct cliente_id is not 7502, but '007502', and when I try to access that confirmacion.cliente, I get a "Cliente matching query does not exist" exception.

I also tried using to_field="codigo", same result.

Am I doing something wrong?. Shouldn't the id be a string since the pk is defined as a charfield?.

Thanks.

[Markus Holtermann]

Looks to me like it is the same underlying problem as shown in #14518 or at least related.

[fiomtec@…]

Ok, I've been doing a bit more testing. It seems that it doesn't have to do with the column being a ForeignKey, but with the db column being a foreign key. I've redefined my model like this:

class Confirmacion(models.Model):
    cliente = models.CharField(db_column='entidad_propietaria', max_length=8)
    fecha_orden = models.CharField(max_length=8)
    [...]other fields[...]

When I query some objects, fecha_orden will always be a string (despite it being a date in the form YYYYMMDD), but cliente will be a string if it's something like 'MADRID', but an integer if it can be converted.

Both columns are defined as varchar(8) not null in the database, the only difference is that entidad_propietaria is a foreign key to another table, and fecha_orden isn't.

[Aymeric Augustin]

Accepting on the basis that the examples clearly demonstrate unexpected behavior.

[Tim Graham]

I don't think we have enough information in the report to reproduce the issue. I tested a ForeignKey to a CharField and didn't have any problems on SQLite or PostgreSQL.

Could it be a problem with sqlserver or the database backend you are using? Please reopen if you can provide more details. A failing test case would be helpful.