Create DB Constraint via Django

Question

I have a Django model which looks like this:

class Dummy(models.Model):
    ...
    system = models.CharField(max_length=16)

I want system never to be empty or to contain whitespace.

I know how to use validators in Django.

But I would enforce this at database level.

What is the easiest and django-like way to create a DB constraint for this?

I use PostgreSQL and don't need to support any other database.

Answer 1

2019 Update

Django 2.2 added support for database-level constrains. The new CheckConstraint and UniqueConstraint classes enable adding custom database constraints. Constraints are added to models using the Meta.constraints option.

Your system validation would look like something like this:

from django.db import models
from django.db.models.constraints import CheckConstraint
from django.db.models.query_utils import Q


class Dummy(models.Model):
    ...
    system = models.CharField(max_length=16)

    class Meta:
        constraints = [
            CheckConstraint(
                check=~Q(system="") & ~Q(system__contains=" "),
                name="system_not_blank")
        ]