I'm using Django 1.8 and have an app with over 100 files in the migration folder. Is there a way in Django without deleting the files to "compress" or "optimise" these migrations so I don't have so many of them?
Have you read this part from the django docs?
Squashing migrations¶
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.
Source: https://docs.djangoproject.com/en/1.8/topics/migrations/
Related
I am removing dead code in my django apps, and realized that one of the functions is being used in an old migration file. What is the correct way to remove this code from the old migration file without causing database issues?
You might try the django squashmigrations command, and see if it recognises and removes the redundancy. More about squashing migrations in the docs.
We have been working on a django project for months. You know for a dev team, migrations conflicts happen many times. I searched a lot to look what others do with this kind of problem and got results:
What really annoys me about Django migrations
django migrations - workflow with multiple dev branches
Django Migrations and How to Manage Conflicts
How to avoid migration conflicts with other developers?
And many other articles about how to avoid and resolve migration conflicts.
I want to know what if we just ignore migration files and just don't commit them?
Any answer is appreciated.
You should not ignore database migrations. The Django documentation makes this pretty clear (emphasis is mine):
The migration files for each app live in a “migrations” directory inside of that app, and are designed to be committed to, and distributed as part of, its codebase. You should be making them once on your development machine and then running the same migrations on your colleagues’ machines, your staging machines, and eventually your production machines.
The fact that you have migration conflicts is an indication that your multiple developers are all creating their migrations at different times, resulting in a different set of files. If you commit the migrations as you should, this will never be a problem.
However, if you plan on squashing migrations (e.g. you expect to have a lot of churn in your database schema during a development cycle), you might wait to commit the migrations until all of your database design work for that cycle is complete. But they should always get committed.
After that, everyone will have the same set of files and no more conflicts.
Many moons ago I used commands like ./manage.py reset appname to DROP and then recreate the database tables for a single App. This was handy for when other developers had inadvertently but manually broken something in the database and you wanted to reset things back without affecting other apps (or needing to go through a lengthy dump/load process).
The advent of Django 1.7 and its builtin migrations support seems to have removed and renamed a lot of these commands and I'm going crosseyed with all the shared prefixes in the documentation. Can somebody spell this out for me?
How do I reset the tables for a single application (one with migrations)?
If your Django migration subsystem is not broken in itself, the normal way to reset an app is to run manage.py migrate <app> zero.
This will run all of the app's migrations backwards, so a few things are noteworthy:
if some of the app's migrations are not reversible, the process will fail. Should not happen normally as Django only creates reversible migrations. You can build irreversible ones yourself, though - usually when you create data migrations.
if some other app has a dependency on this app, it will also be migrated backwards up to the last migration that did not depend on it.
You can then run migrate again, so it is run forwards.
In any case, remember migrations introduce a risk for your data, so backup your database before touching anything.
I'm using Django 1.8 and have an app with over 100 files in the migration folder. Is there a way in Django without deleting the files to "compress" or "optimise" these migrations so I don't have so many of them?
Have you read this part from the django docs?
Squashing migrations¶
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.
Source: https://docs.djangoproject.com/en/1.8/topics/migrations/
Our product has a restful API and a server rendered app (the CMS). Both share the database. Both are written in django
The fields and the models needed in both are not mutually exclusive, there are some only particular to the API, some particular to the CMS, and some which are common.
My question is if I run migrations on one of the repos will they try to drop the fields that aren't present in the models of that particular repo, and needed by the other. Will running the migrations individually in both repos keep the database up to date and not pose a problem.
The only other valid option IMHO (besides merging projects) is turning off automation of Django migrations on common models (Meta.managed = False) and taking table creation & versioning into your own hands. You still can write migration scripts using django.db.migrations but makemigrations command won't do anything for these tables.
This was solved by using a schema migration tool external to Django's own. We use
yoyo migrations to migrate our schema now.
Will running the migrations individually in both repos keep the database up to
date and not pose a problem.
Unfortunately, no. As you suspected, changes in one will attempt to override the other.
The easiest thing to do is merge the two projects into one so this problem goes away entirely.
If this isn't an option, can the code be organised in such a way that both projects share the same models.py files? You could do this by perhaps having the models.py files and migrations folders only exist in one project. The second project could have a symlink across to each models.py file it uses. The trick (and the difficult part) will be to make sure you never create migrations for the app which uses the symlinks.
I think the best things to do would be to have one repo that contains all the fields. This project will be responsible to apply the migrations.
In the other projects, you'll need a db_router containing a function allow_migrate which will return False on your model classes.
Also having different db user with different db permissions can prevent from altering the tables.