Custom South migration with custom fields - Django - database

Question

I am pretty new to Django and just got a job that involves maintaining and adding features to a site I did not design, so I am still kind of confused about the structure and what not of the project. The site is using South for database migrations and I've got a hang of using it to add new applications to the project. The trouble I am having now is that I need to delete a certain field in a model because it is no longer needed and on the admin page it is required to be filled out. From my understanding of Django so far it appears to be a custom field. It is defined like this in its own separate library application(still not sure if thats the right lingo).
class Genre(models.Model):
name = models.CharField(max_length=255)
def __unicode__(self):
return u"%s" % self.name
Here is the models that uses the custom field if that helps out any.
class Entry(models.Model):
artist = d51fields.ForeignKey(Artist, instantiate_fn=instant_artist)
album = d51fields.ForeignKey(Album, js_methods=['match_artist_and_startswith'], instantiate_fn=instant_album)
track = d51fields.ForeignKey(Track, js_methods=['match_album_and_startswith'], instantiate_fn=instant_track)
genre = models.ForeignKey(Genre)
submitted = models.DateTimeField(auto_now_add=True)
is_rotation = models.BooleanField()
dj = models.ForeignKey(DJ)
show = models.ForeignKey(Show, null=True, blank=True)
objects = EntryManager()
def __unicode__(self):
return "%s [%s]" % (self.artist, self.track)
class Meta:
verbose_name = "entry"
verbose_name_plural = "entries"
I've looked at the documentation for migrating custom fields but it is all really confusing for me, so I am looking for some more help. I just want to get rid of the table holding the Genre field and clean up the dependencies with the foreign keys associated with it. Do you think I should write some custom rules for South and use a migration or just try and do it manually in Postgresql. I tried doing it with just Postgres and I failed miserably.
Any guidance would be greatly appreciated. If you want more info about the situation just ask and I can add it to the post. I have a feeling there is a lot of dependencies I will have to deal with, but hopefully there is a simple fix.
Also if some one knows how to get a good view of the database structure that would be great.
Thanks so much. All of you guys are great.
Edit1
Here what I got when I removed the ForeignKeys and then ran
manage.py schemamigration logs --auto
! Cannot freeze field 'logs.entry.artist'
! (this field has class d51_admin_autofk.fields.ForeignKey)
! Cannot freeze field 'logs.entry.album'
! (this field has class d51_admin_autofk.fields.ForeignKey)
! Cannot freeze field 'logs.entry.track'
! (this field has class d51_admin_autofk.fields.ForeignKey)
! South cannot introspect some fields; this is probably because they are custom
! fields. If they worked in 0.6 or below, this is because we have removed the
! models parser (it often broke things).
I am not totally sure what sort of action I should take next. I looked into the South documentation and it wasn't too clear about how to write the rules for migrating things like this.

Answer 1

I don't see any custom field anywhere in the code you posted. All I see is two models, all containing standard fields shipped with Django.
If I understand correctly, you can just delete all ForeignKey references to your Genre model. Then run ./manage.py schemamigration <yourappname> --auto. This will ask you for a default value for the genre field in the Entry model, provide an ID of some kind. (This is because migrations can be applied both forwards and backwards, so if you try to undo the migration, this is the value that will get inserted in all your model instances.)
Finally, just applying the migration should make it happen: ./manage.py migrate <yourappname>.
After that you should be safe to drop the table storing your Genre model.
Be sure to try this on a development server though, just to make sure it doesn't blow up. (-;