Django primary key error (Djongo driver)

Question

I'm writing a website on Python, Django using MongoDB and Djongo (to connect Mongo with Django) and I want to be able to add and delete documents from the database using my website. But I have an error while doing it.

If I don't set primary key in my models then I can successfully add documents, but when try to delete have AssertionError (object can't be deleted because its id attribute is set to None), however when I check the database _ID field is there created automatically. If I do set primary key by primary_key = True in models.py I can successfully delete a document, but on insertion I got AssertionError (No exception message supplied).

Also, if primary key is not set, then I cannot access documents from admin panel, but can add them to the database (through admin panel); and if pk is set then from admin panel I can access, delete and edit, but cannot add a new document to the database.

This is my model:

class DevList(models.Model):
    dev_num = models.CharField(max_length = 200 , primary_key = True)
    dev_name = models.CharField(max_length = 200)
    dev_descr = models.CharField(max_length = 200)
    dev_type = models.CharField(max_length = 200)

If no pk is set, then I delete primary_key = True line

My view is simple post form and I use d.save() to save and d.delete() to delete.

Answer 1

Actually, Django by default provides an id field with every model which is by default set as primary key.

Now, when you can set other field as primary key by primary_key=True. But for smoother operation I will advice you to use unique=True on other fields.

dev_num = models.CharField(max_length = 200 , unique = True)

Answer 2

I had a similar problem using MongoDB + Django with the Djongo driver (cannot delete objects in the admin page of my website because the _id is not an integer but an ObjectID() wich is not recognized as a valid integer).

This is how I solved it (the quickest way) : I set for my object an id with the models.PositiveIntegerField type and I use the primary_key argument with the True value) :

class MyObject(models.Model):
    id = models.PositiveIntegerField(primary_key=True)
    title = models.CharField(max_length=100)
    other_field = models.TextField(blank=True)

    def __str__(self):
        return f"{self.title}"

This way, the _id of mongoDB is not used but the admin system still find a valid integer for the primary key. That has been tested succesfully, problem solved.