Why does Django ORM allow me to omit parameters for NOT NULL fields when creating an object?

Question

Stupid question time. I seem to be able to create an object for a Django model even though I omit a column that was defined as NOT NULL and I don't understand why. Here's my model:

class Movie(models.Model):
    name = models.CharField(max_length=256)
    length_minutes = models.IntegerField()
    rating = models.CharField(max_length=2)

    class Meta:
        db_table = 'movies'

When I run python manage.py sql I see:

BEGIN;
CREATE TABLE "movies" (
  "id" serial NOT NULL PRIMARY KEY,
  "name" varchar(256) NOT NULL,
  "length_minutes" integer NOT NULL,
  "rating" varchar(2) NOT NULL
);
COMMIT;

Also, if I run the command \d movies from the psql, I can see that all columns are designated NOT NULL.

But here's what I don't understand. When I run the Python shell, I can issue the following command and a new row with an empty 'name' column will be created:

Movie.objects.create(length_minutes=120, rating='PG')

However, if I issue (what I believe to be) the equivalent SQL command:

INSERT INTO movies(length_minutes, rating) VALUES(120, 'PG');

... I get the error I would expect: "ERROR: null value... violates not-null constraint."

Why does Django's ORM allow me to create an object that lacks a parameter for a NOT NULL CharField column? Does it assume that I'm using model validators? If so, it seems to be a pretty dumb and trusting ORM.

I'm using Python 2.7.1, Django 1.4, and PostgreSQL 9.1.4.

Thanks for your help.

Answer 1

After a great deal of online research and experimentation, what I've found indicates that the behavior I described above is normal Django behavior. Apparently, Django doesn't validate models by default. Furthermore, the default value for a CharField is the empty string. In order to ensure that Django raises the expected IntegrityError if I omit a CharField parameter designated NOT NULL, I needed to add "default=None" to the signature declaration:

name = models.CharField(max_length=256, default=None)

Can I get credit for answering my own question?