Django ORM model default not applying in python queryset

Question

I have the below Django ORM which represents a PostgreSQL view.

For the field cost_requirement I have set the default value to 0. However the queryset object still populates with None if data is missing for this field.

I have made all migrations and I just want the default to apply at the Python side (nothing to do with the database). From the Django documentation I understand I am using this argument correctly.

Any suggestions why the default value of 0 is not being applied?

class DashboardProduct(models.Model):
    date = models.DateField()
    product_id = models.CharField(max_length=50)
    base_l = models.FloatField(default=0)   
    cost_requirement =  models.FloatField(blank=False, null=False, default=0)
    book = models.CharField(max_length=100, blank=True, null=True)
    portfolio = models.CharField(max_length=100, blank=True, null=True)
    sales_5_pnl = models.FloatField(default=0)   
    

    class Meta: 
        managed = False 
        db_table = 'view_dashboard_product'

Answer 1

the default=… ^[Django-doc] is when you create records, but you here work with a view, so it does not create anything, it will thus keep the results from the query. It does not use default=… as a fallback for NULL.

You can use coalesce in the query, like:

from django.db.models import Value
from django.db.models.functions import Coalesce


class DashboardProductManager(models.Manager):
    def get_queryset(self, *args, **kwargs):
        return (
            super()
            .get_queryset()
            .annotate(cost_requirement=Coalesce('_cost_requirement', Value(0)))
        )


class DashboardProduct(models.Model):
    date = models.DateField()
    product_id = models.CharField(max_length=50)
    base_l = models.FloatField(default=0)
    _cost_requirement = models.FloatField(
        db_column='cost_requirement', blank=False, null=False, default=0
    )
    book = models.CharField(max_length=100, blank=True, null=True)
    portfolio = models.CharField(max_length=100, blank=True, null=True)
    sales_5_pnl = models.FloatField(default=0)

    objects = DashboardProductManager()

    class Meta:
        managed = False
        db_table = 'view_dashboard_product'