delete() does not function consistently with CharField PKs

[w004dal]

I'm working with MyISAM tables with MySQL and have the following behavior with delete() on Django 1.2.3-1 on Fedora Core 12.

class DoesWork(models.Model):
    mac_id = models.CharField(max_length=17)
    ip = models.CharField('Host/IP Address', max_length=255)

class DoesNotWork(models.Model):
    mac_id = models.CharField(max_length=17, primary_key=True)
    ip = models.CharField('Host/IP Address', max_length=255)

The following works as expected, creating, deleting, and putting the item back:

zz = DoesWork.objects.create(mac_id='99:99:99:99:99:99', ip='127.0.0.1')
zz.delete() # remove from DB
zz.save() # it's back in the DB

However, if I use the DoesNotWork model, whose only difference is having a CharField as a primary key:

zz = DoesNotWork.objects.create(mac_id='99:99:99:99:99:99', ip='127.0.0.1')
zz.delete() # remove from DB
zz.save() # EXCEPTION THROWN:

IntegrityError: (1048, "Column 'mac_id' cannot be null")

I checked by printing out zz.__dict__, and the mac_id was 'None' with the DoesNotWork object, but was untouched with the DoesWork object.

[Russell Keith-Magee]

Corrected formatting. Please use preview.

[Russell Keith-Magee]

This is working as expected. When you delete the object, it's primary key is set to None. In the model DoesNotWork, the primary key is manually allocated, so subsequent saves are prevented. In the model DoesWork, the primary key is automatically allocated, so a new object is inserted.

[w004dal]

What is the expected behavior for the class below? DoesWork should be syntactic sugar for DoesNotWorkToo:

class DoesNotWorkToo(models.Model):
    some_key = models.IntegerField(primary_key=True)
    mac_id = models.CharField(max_length=17)
    ip = models.CharField('Host/IP Address', max_length=255)

[Russell Keith-Magee]

If you have questions, please ask them on django-users.

[w004dal]

Please reopen this bug to at least improve the documentation on ​http://docs.djangoproject.com/en/dev/topics/db/queries to include this subtlety.