django-unmigrate 0.1.4

Smart reversion of Django migrations based on Git diff

If you are in a complex Django project, sometimes you will find yourself switching between multiple branches, some of which can add a number of database migrations. Before switching back to master you will have to unapply all migrations that are specific to the current branch. In order to unapply these, you will have to enter the migration that comes right before the first migration of the current branch. If two or more apps are involved, you will have to do that for each one of them.

If you leave your migration names unchanged, inferring the name of the right migration to target is not too difficult, because they are prefixed by default with a sequential number. Django also helps, being smart enough to let you use an unambiguous prefix of any migration name. Add a merge migration and the numbers will no longer be so obvious. Or if you have renamed your migration files as this article recommends, you will have to do the search manually.

With django-unmigrate you can speed up the process.

Usage

Add django-unmigrate to your INSTALLED_APPS. This is required to make the unmigrate management command available.

Then, while standing on any branch, you will be able to use:

python manage.py unmigrate master

Or if it’s going to be master anyways, this will suffice:

python manage.py unmigrate

And that’s it!

A little deeper

Ok, you can do more than that.

Do you need to unapply your migrations from the same branch, a few commits behind? Here’s how:

python manage.py unmigrate HEAD~12
python manage.py unmigrate b13553d
python manage.py unmigrate v1.33.7

Or if you only want to see the target migrations, do:

python manage.py unmigrate --dry-run

Finally, if you just want to play with the app with no actual modifications in the database, go ahead and unapply your migrations with fake. Just don’t forget to apply them again at the end:

python manage.py unmigrate --fake
python manage.py migrate --fake

Do you see potential?

This app started as a quick-n-dirty hack to speed up my team’s development in multiple Django projects. However, with your help, it can become more than that:

• Do you find the migration diff detection code hackish? We agree, help us make it more robust and aligned with the Django internals.

• Do you use mercurial instead of git? Help us with a mercurial adapter. Maybe another VCS? Please, help us as well!

• Do you think this app can be used as a tool to generate automatic rollback scripts for automatic Django deployments? We’re thinking the same. Help us shape the logic and give us a hand with the code!

• Is there any other direction where you see potential here? We’re open to hear your ideas.

Contributing

• Join the discussion at https://gitter.im/django-unmigrate/community.

• PRs are welcome! If you have questions or comments, please use the link above.

• To run the test suite run make or make coverage. The tests for this project live inside a small django project called dunm_sandbox. Beware! This package uses Git to function, therefore, the tests expect a number of commit hashes inside this repository to be present and remain stable in order to function. See this meta file for further details.