What’s the recommended approach to resetting migration history using Django South

djangodjango-south

I've accumulated quite a few migrations using South (0.7) and Django (1.1.2) which are starting to consume quite a bit of time in my unit tests. I would like to reset the baseline and start a fresh set of migrations. I've reviewed the South documentation, done the usual Google/Stackoverflow searching (e.g. "django south (reset OR delete OR remove) migration history") and haven't found anything obvious.

One approach I've contemplated would involve "starting over" by "removing" South or "clearing" the history manually (e.g. clear the db table, remove migration files from the migrations director) and just re-run,

./manage.py schemamigration southtut –initial

So, if anyone has done this before and has some tips/suggestions they would be greatly appreciated.

Best Answer

If you need to selectively (for just one app) reset migrations that are taking too long, this worked for me.

rm <app-dir>/migrations/*
python manage.py schemamigration <app-name> --initial
python manage.py migrate <app-name> 0001 --fake  --delete-ghost-migrations

Don't forget to manually restore any dependencies on other apps by adding lines like depends_on = (("<other_app_name>", "0001_initial"),("<yet_another_app_name>", "0001_initial")) to your <app-dir>/migrations/0001_initial.py file, as the first attribute in your migration class just below class Migration(SchemaMigration):.

You can then ./manage.py migrate <app-name> --fake --delete-ghost-migrations on other environments, per this SO answer. Of course if you fake the delete or fake the migrate zero you'll need to manually delete any left-over db tables with a migration like this.

A more nuclear option is to ./manage.py migrate --fake --delete-ghost-migrations on the live deployment server followed by a [my]sqldump. Then pipe that dump into [my]sql on the environments where you need the migrated, fully-populated db. South sacrilege, I know, but worked for me.

Related Solutions

Python – Django – How to rename a model field using South

You can use the db.rename_column function.

class Migration:

    def forwards(self, orm):
        # Rename 'name' field to 'full_name'
        db.rename_column('app_foo', 'name', 'full_name')




    def backwards(self, orm):
        # Rename 'full_name' field to 'name'
        db.rename_column('app_foo', 'full_name', 'name')

The first argument of db.rename_column is the table name, so it's important to remember how Django creates table names:

Django automatically derives the name of the database table from the name of your model class and the app that contains it. A model's database table name is constructed by joining the model's "app label" -- the name you used in manage.py startapp -- to the model's class name, with an underscore between them.

In the case where you have a multi-worded, camel-cased model name, such as ProjectItem, the table name will be app_projectitem (i.e., an underscore will not be inserted between project and item even though they are camel-cased).

Backwards migration with Django South

You need to figure out the number of the migration just before the one you want to roll back.

Your app should have a migrations directory, with files in it named like

0000_initial.py
0001_added_some_fields.py
0002_added_some_more_fields.py
0003_deleted_some_stuff.py

Normally, when you run ./manage.py migrate your_app, South runs all new migrations, in order. (It looks at the database tables to decide which ones are 'new').

However, you can also specify any migration by number, and South will migrate your database, either forward or backward, to take it to that point. So, with the example files above, if you have already migrated up to 0003, and you wanted to run 0003 in reverse (undoing it, effectively), you would run

./manage.py migrate your_app 0002

South would look at the database, realise that it has run 0003 already, and determine that it has to run the reverse migration for 0003 in order to get back to 0002.

Best Answer

Related Solutions

Python – Django – How to rename a model field using South

Backwards migration with Django South

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