Question

I have a couple of tables that are joined by GUIDs in SQL Server. Now, I’ve found a few custom fields to add support for GUIDs in django, but I tend to shy away from using code in blog posts if at all possible. I’m not going to do anything with the GUID other than join on it and maybe assign a GUID on new entries (although this is optional). Is there any way to allow this using django’s built-in types? Like can I use some kind of char field or binary field and “trick” django into joining using it?

If it’s any help, I’m using django-pyodbc.

Answer 1

I’d create a basic GUID Model in order to reuse it’s properties for any other models in my projects. Model inheritance is working nicely since several versions prior to Django 1.0 and is quite stable with Django 1.0.

Create something like project/common/models.py and place there this class:

import hashlib
import random
from django.db import models

class GUIDModel(models.Model):

    guid = models.CharField(primary_key=True, max_length=40)

    def save(self, *args, **kwargs):

      if not self.guid:
        self.guid = hashlib.sha1(str(random.random())).hexdigest()

      super(GUIDModel, self).save(*args, **kwargs)

Then create your other models as usual:

from common.models import GUIDModel

class Customer(GUIDModel):
  name = models.CharField(max_length=64)

class Product(GUIDModel):
  name = models.CharField(max_length=64)

class Sale(GUIDModel):
  customer = models.ForeignKey(Customer)
  product = models.ForeignKey(Product)
  items = models.PositiveIntegerField()

And everything should work nicely with GUIDs as primary keys instead of autoincremental integers.