Django: Safely Remove Old Migrations?

Question

I've got a Django app with a lot of out-of-date migrations. I'd like to remove the old migrations and start fresh.

The app has 14 different "migrations" folders.

Here is what a few of them look like:

Is it safe to remove all the contents from each of these folders? Or, do I have to make sure to only remove some of the files -- and if so which files?

Answer 1

You should never just delete migrations before unapplying them, or it will be a nightmare when you want to apply new migrations.

To unapply migrations you should do the following:

1. Use the python manage.py migrate your_app_name XXXX in case you want to unapply migrations after the XXXX migration. Otherwise use python manage.py migrate your_app_name zero to completely unapply all migrations.

2. Remove the .pyc files under /migrations/_pycache_/ that you have unapplied.

3. Remove the .py files under migrations/ that you have unapplied.

Now you can create new migrations without any headaches.

If what you're looking for is to squash all the migrations into one, do the steps above removing all migrations and then run python manage.py makemigrations your_app_name to create a single migration file. After that just run python manage.py migrate your_app_name and you're done.

Answer 2

That depends. If you have a production database (or any database you cannot simply drop and recreate), then the answer is no, you cannot safely remove migrations.

If you do not have any permanent databases, then yes, you can remove all migrations, run python manage.py makemigrations --initial and it will create fresh migrations based on your current models.

Also, you should check if any of the migrations are custom data migrations written by hand. If there are any, you might want to keep those.

The .pyc files are generally safe to remove, provided the related .py files are still there.

your first screenshot is not Django and looks like a JS project of some sort.

Answer 3

1. The json and js files are unrelated to the django migrations as well as __pycache__ folder. You can delete all off them.
2. If you mean "previously applied and no longer needed as the project only needs the latest version of the migrations" you don't want to remove but squash them instead with squashmigrations which reduces the files you have to two, init file and the initial migration file, this way your project still works.
3. If by remove you mean you no longer need them because you already changed the models so much that the previous migrations aren't even used other than being applied and unapplied without ever being used, doesn't matter, go to step 2 and do that instead of deleting the files manually. When you create migrations on your applications one by one, you also create migration dependency tree, well, django does. And it is really hard to keep track of after some point, if you try to delete everything thinking you can create new migration files with ease, trust me as someone who experienced otherwise, it does not work like that. It is way simpler to let django handle the migration squashing, it optimizes the migration meaning that it also deletes the unused ones in your final state.

More to read at: https://docs.djangoproject.com/en/2.2/topics/migrations/#migration-squashing