问题
I personally like django for its MVC ideals. But while i am running Django migrations in version 1.7 each and every migrations i do in it is stored inside the migrations directory. If i delete those file it is throwing an error while migration.
I Tested like this. I created a new Django project and initiated a git repo . I ran some 3-4 migrations in Django which resulted in 3-4 migration files under the migrations directory. I tried deleting the very older migration files i.e (1st and 2nd migration files) and tried to run
python manage.py makemigrations
which does cause some error like "migration files not found". Later i did a git stash which restored the deleted files. Now i tried to run the same command again and it was working fine.
What my question is if a person runs some 50 changes in db during development all the migration files are stored in migrations directory. Is it possible to delete those files and do changes to db again without any interruption?
回答1:
The answer is "it depends".
If you are working against a production DB, or some DB that can't periodically blow away for whatever reason, then you absolutely want to keep around the migration files that you've applied to your DB. They should be checked into source control with the rest of your code.
Now, for a situation like yours, the easiest way to discard your 50 migrations would be to just blow away the db (and it's 50 migrations) and start from scratch given your current models. It's oftentimes a good idea to do this periodically as you evolve your models during development.
Its ok to blow away your models when you blow away your DB because syncdb will build a blank db using your current models. It'll then optionally populate the db using any initial fixtures. Conceptually, there is no longer anything that you've migrated from at such a point, so you don't need to keep around your old migrations for your old db. They are no longer relevant.
It's not usually good to delete migration files that have been applied to your DB unless you are either 1) blowing away the DB altogether, or 2) reverting the migrations first.
You might also appreciate knowing that when you apply migrations to a db it's also recording those migrations in a special table in the db itself. That's why things go haywire when you just delete the migration files. They have to stay in sync with the migration table
回答2:
If you want to keep your DB, but decrease the number of migration files, one option is squashing the migrations into one (or few, if complex dependencies) migration.
From the official documentation:
You are encouraged to make migrations freely and not worry about how many you have; the migration code is optimized to deal with hundreds at a time without much slowdown. However, eventually you will want to move back from having several hundred migrations to just a few, and that’s where squashing comes in.
Before squashing, you should be aware that "model interdependencies in Django can get very complex, and squashing may result in migrations that do not run", and therefore manual work may be needed.
For detailed information about how to make the squashing, refer to the docs: https://docs.djangoproject.com/en/dev/topics/migrations/#squashing-migrations
回答3:
The answer is "Do not delete migration files".
To understand why we shouldn't delete migration files, you need to understand how migration works in frameworks.
Migration files are the history of your database. One migration file is created based on the migration files created in the past. Deleting migration files means losing your history. This historical info is recorded in the django_migrations table in your database. if you delete migration files, you will get dependency errors. So Don't try to lose your history by deleting your migration files.
来源：https://stackoverflow.com/questions/28404461/can-i-delete-the-django-migration-files-inside-migrations-directory