How to set a custom field in a Django session model?

Question

I have extended the session in Django per this. In short, I have added a field named account_id to hold the user id of the user which the session belongs to.

Everything works fine, except the custom field account_id I have added is not being set on login. To do so:

from django.contrib import auth
from MyApp.models import CustomSession

def login(request):
    username = request.POST['username']
    password = request.POST['password']
    user = auth.authenticate(username=username, password=password)
    if user is not None:
        try:
            auth.login(request, user)
            session_key = request.session.session_key
            # CODE HERE
            if session_key is not None:
                return HttpResponse(json.dumps({'status': 'Success'}))
            else:
                return HttpResponse(json.dumps({'status': 'Fail'}))

I have tried putting the following to CODE HERE. However, none of them worked:

1. request.session.model.account_id = user.id

2. session = CustomSession.objects.get(pk=session_key)
   session.account_id = user.id
   session.modified = True
   

3. request.session.account_id = user.id
4. request.session[account_id] = user.id

In each of these attempts, account_id is NULL in the data base.

What am I missing here?

Answer 1

If you want to give a custom name or create a custom field in the session table, you can follow the following step.

Define a custom session backend:

my_project
    my_project/
        settings.py
        session_backend.py
        ...
    user/
        models.py
        ...

from django.contrib.sessions.backends.db import SessionStore as DBStore
import user


class SessionStore(DBStore):

    @classmethod
    def get_model_class(cls):
        return user.models.MySession

    def create_model_instance(self, data):
        """
        overriding the function to save the changes to db using `session["user_id"] = user.id` .
        This will create the model instance with the custom field values. 
        When you add more field to the custom session model you have to update the function 
        to handle those fields as well.
        """
        obj = super().create_model_instance(data)
        try:
            user_id = data.get('user_id')
        except (ValueError, TypeError):
            user_id = None

        obj.user_id = user_id
        return obj

then in settings.py import your custom class

SESSION_ENGINE = "my_project.session_backend"

Define the custom model in models.py in the app say user

from django.contrib.sessions.models import Session


class MySession(Session):
    # you can also add custom field if required like this user column which can be the FK to the user table 
    user = models.ForeignKey('user', on_delete=models.CASCADE) 

    class Meta:
        app_label = "user"
        db_table = "my_session"

now run the following commands for migrations

python manage.py makemigrations
python manage.py migrate

Done :)

Answer 2

You're missing the fact that CustomSession is a model; you need to save the instance, not set "modified" on it as you do in version 2.

session = CustomSession.objects.get(pk=session_key)
session.account_id = user.id
session.save()