Using a UUID as a primary key in Django models (generic relations impact)

mitchf picture mitchf · Oct 14, 2010 · Viewed 47.8k times · Source

For a number of reasons^, I'd like to use a UUID as a primary key in some of my Django models. If I do so, will I still be able to use outside apps like "contrib.comments", "django-voting" or "django-tagging" which use generic relations via ContentType?

Using "django-voting" as an example, the Vote model looks like this:

class Vote(models.Model):
    user         = models.ForeignKey(User)
    content_type = models.ForeignKey(ContentType)
    object_id    = models.PositiveIntegerField()
    object       = generic.GenericForeignKey('content_type', 'object_id')
    vote         = models.SmallIntegerField(choices=SCORES)

This app seems to be assuming that the primary key for the model being voted on is an integer.

The built-in comments app seems to be capable of handling non-integer PKs, though:

class BaseCommentAbstractModel(models.Model):
    content_type   = models.ForeignKey(ContentType,
            verbose_name=_('content type'),
            related_name="content_type_set_for_%(class)s")
    object_pk      = models.TextField(_('object ID'))
    content_object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_pk")

Is this "integer-PK-assumed" problem a common situation for third-party apps which would make using UUIDs a pain? Or, possibly, am I misreading this situation?

Is there a way to use UUIDs as primary keys in Django without causing too much trouble?


^ Some of the reasons: hiding object counts, preventing url "id crawling", using multiple servers to create non-conflicting objects, ...

Answer

keithhackbarth picture keithhackbarth · Feb 12, 2015

As seen in the documentation, from Django 1.8 there is a built in UUID field. The performance differences when using a UUID vs integer are negligible.

import uuid
from django.db import models

class MyUUIDModel(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

You can also check this answer for more information.