Problem when migrating with Python and Django: no such column: forum_thread.Slug

Question

I have this problem in my code:

OperationalError at /admin/forum/thread/ no such column: forum_thread.slug

I’ve tried to make a million changes and I couldn’t. When I turn the command python manage.py makemigrations returns the following error message:

You are trying to add a non-nullable field 'Slug' to thread without a default; we can’t do that (the database needs Something to populate existing Rows). Please select a fix: 1) Provide a one-off default now (will be set on all existing Rows) 2) Quit, and Let me add a default in models.py Select an option:

Down with my models.py:

https://github.com/MarcusWiilo/Django-Aplications/blob/master/pro_final/pro_final/forum/models.py

The complete file is here:

https://github.com/MarcusWiilo/Django-Aplications/tree/master/pro_final

Thanks.

Answer 1

The message says that you are adding a "non-nullable" field, in a database that already has records, but you have not set a default value for that field. The message gives you 2 options: 1) to inform a default value for this field or to "abort" the operation and fix the problem in the model. You must do one of the two, enter a default value or go to your model and add in the field:

slug = models.SlugField(...., null=True, blank=True)

With this you can create the field, then make the necessary changes, and then false these two parameters, if necessary.

Or you could have entered a default value for the field, like this:

slug = models.SlugField(...., default='Valor default blah blah')

If the bank is testing, it might be more convenient to exclude the bank, the migrations and rebuild it.