Slugfield in tango with django

Question

I'm reading this tutorial to lear the basics of django and I'm facing a problem I can't solve.

I'm at this page http://www.tangowithdjango.com/book17/chapters/models_templates.html at the sluglify function approach.

In the tutorial the author says we have to create a new line in our category model for th slugfield. I folow strictly all the steps just as I show here:

from django.db import models
from django.template.defaultfilters import slugify

class Category(models.Model):
    name = models.CharField(max_length=128, unique=True)
    likes = models.IntegerField(default=0)
    views = models.IntegerField(default=0)
    slug = models.SlugField(unique=True)

    def __unicode__(self):
        return self.name

class Page(models.Model):
    category = models.ForeignKey(Category)
    title = models.CharField(max_length=128)
    url = models.URLField()
    views = models.IntegerField(default=0)


    def __unicode__(self):
        return self.title

When I run the "makemgiration" command everything works as expected: I choose the first option and provide ‘’ . BUT when I run "migrate" I get:

django.db.utils.Integrity error: Slug column is not unique

What is going on here? I've repeated several times the migrations and tried other default codes but with the same ending. I can't figure out what im doing wrong. They only thing left is that i'm giving something else instead of ‘’ (Firstly I thoughtthey were '' or ").

Thankyou for your time and help!

Answer 1

Delete db.sqlite3 and re run

python manage.py syncdb

Then perform the migrations

python manage.py makemigrations rango
python manage.py migrate

and re run your population script. This is a downside of Django that whenever you change models.py the db must be recreated.

Answer 2

I am also going through the tutorial and I was having the same issue a couple days ago.

I believe the problem is that you are trying to add a new field (slug) and have it be unique for each of the elements in your table but if I'm not mistaken you already have some data in your table for which that value does not exist and therefore the value that this field would get for those rows is not unique, hence the "django.db.utils.Integrity error: Slug column is not unique".

What I did was simply to delete the data in the table (because it was only a couple of fields, so no big deal) and THEN perform the addition of the field to the model. After doing that, you can put the data back in the table (if you're following the tutorial you should have a script for automated table population so you just run that script and you're golden). Once you have done that, all the rows in the table should have a unique slug field (since it is automatically generated based on the category name) and that solves the problem.

Note that if your table is very large, this may not be a very good solution because of the deletion of data so perhaps there is a better way, like adding that field to the model without it being unique, then running a script that sets the slug field for every row to an unique value and then setting the model's field as unique but I'm not very knowledgeable on SQL and the first solution worked just fine for me so it should work for you as well.

Answer 3

try deleting the sqlite3.db file from the project's directory. i was stuck on a similar problem and that really works..also even if you modify your population script, you have to delete and the recreate the db file to see the changes made....