I've deployed my Django application for a while now, but all this time I've kept migrations out of souce control. What I did was run makemigrations and migrate twice-- once in development, and once in production. So now how can I seamlessly put my migrations into source control? Theoretically the migrations should be the same (given my models.py files haven't changed), but how would I go about matching my migrations up without accidentally overriding something?
I'm not sure if I understand the problem...
Django keeps track of which migrations have been applied using the database. But it uses the names, not the contents. So as long as you're not changing the contents of migrations that have already been applied, you should be good.
Related
I am a beginner using Django. I have recently been working on a website that has a few different pages. I reference a couple of views from other apps in urls.py. One app I used to take inputs and make some calculations, so it had some forms defined. It was all working fine and I was able to import the views fine, but I changed one of my form field names. This caused some problems because I was storing these values in a database. That made sense to me because I had already saved some data with the previous naming convention and now I had changed it. So, I figured that deleting my database and migrations would allow me to start over and start a new database with my updated fields. I messed up though because I read that I should not have deleted my init.py file in my migrations folder.
I have tried re-doing my migrations with makemigrations and migrate but I keep getting an error saying that no changes are made and no new migrations show up in my folder. Also, now when I look in my urls.py file, the imported views and apps are showing up with a red underline and says "import package".
I have also tried reverting my code back and was able to get the migration files back, but the same error was shown in my urls.py file.
I have tried just about everything I could find online, but am now thinking that I may just have to recreate these apps.
Any help is appreciated!
First of all, to rename a form field, just change it in the models and then make and apply migrations. Django should detect the renaming of an existing field and create migrations.AlterField(...) statements (you can inspect the migration files that were created, and freely delete them if they are not yet applied/migrated).
First, please check if adding the empty file called __init__.py to the migration folder solves the problem. This is a python requirement, to let the interpreter know that the folder contains a python module.
Also if you have downloaded the project from somewhere, you need to have the existing migrations. Deleting them and recreating them yourself will likely fail.
After that just try running
python manage.py makemigrations
python manage.py migrate
If there are still no changes, check if there are migrations applied to your database by looking at the django_migrations table or by running this command:
python manage.py showmigrations
If this did not help, try to start with a clean project:
Backup all your code changes and revert to the starting point, the __init__.py file should be back and you should also delete the database (db.sqlite3)
run the migrate command
add all your code changes
check if your code changes have new migration files, they could cause problems. If you have not created or modified them manually, you can delete and let Django recreate them
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?
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:
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.
Remove the .pyc files under /migrations/_pycache_/ that you have unapplied.
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.
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.
The json and js files are unrelated to the django migrations as well as __pycache__ folder. You can delete all off them.
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.
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
Having marked one of the answers provided previously as being accepted, here is a summary of a few things I learned:
Deleting Django migrations is generally a bad idea.
Django keeps track of what's in your db through these migration files, as well as through a table it creates in your db, and if you delete any of this Django will start throwing errors on migrate that can be hard to fix.
I was getting some of those hard-to-fix errors. Here is what I did to fix it:
Ran migrate on the production server.
When I got an error, it would tell me how the db was out of sync with what Django expected. I corrected that manually by directly editing the db with an sql client.
E.g. If it said a key existed that wasn't supposed to exist, I deleted the relevant index from the indicated table.
Or if it said a table existed that wasn't supposed to exist, I backed up the table to a file, and deleted the table. Migrate then created the table, and then I repopulated it with data from the backup.
In the case of many-to-many tables, once Django had re-created them, I deleted all the new Django-created tables, and restored them from a backup created on my local dev system, which had already had all the latest migrations run on it.
Eventually I was able to complete all migrations successfully.
I have a feeling I lucked out and the above won't work in all cases! I've learned a lot about Django and migrations and will be much more careful about this in the future.
when you import from third app:
there are 2 step uninstall it
there are use the 'django_celery_beat' app for example.
step1: clean table
python .\manage.py migrate django_celery_beat zero
step2: remove app from INSTALLED_APPS
there are done!!!
this is django document on this.
How to Reset Migrations
if you are using linux/unix os then you can fire this command. delete all migration directory.
find . -path "/migrations/.py" -not -name "init.py" -delete
find . -path "/migrations/.pyc" -delete
I have a Postgres database full of data. And I made several changes to my Django app models.
mange.py makemigrations worked fine and created the migration files. But manage.py migrate execute only one file. And when I launch it again it doesn’t execute the rest as if they are already applied.
I deleted the migration files that were not applied and did another makemigration but it says no changes detected.
Any ideas how to reflect the models changes on the database without losing the data ?
Thanks
Django keeps track of which migrations it has applied already, so when you run the migrate command it will execute only the migrations that Django thinks that are missing.
I deleted the migration files that were not applied and did another makemigration but it says no changes detected.
This was a bad idea, it will make your migrations inconsistent.
If you want to go back in time, instead of deleting migrations, the proper way to do this is by reverting migrations. You can use the same migrate command and specify to which migration point you want your database model to be.
Check this answer for further information about reverting migrations; django revert last migration
We are a team of developers working on Django project. We are facing issues with django migrations. if one developer makes changes in model and runs makemigrations>migrate sequence it generates some sqls in migrations directory. Now when other developer pulls the code, and run the same sequence it's putting code in bad state. We've been clearing our migrations directory locally to get rid of the issue, and sometimes clear all the data. Not sure what we're doing incorrectly. Please suggest the right way of using django migrations.
Note - All of us use separate instances of DB in local machine.
makemigrations just create files
By running makemigrations, you’re telling Django that you’ve made some changes to your models (in this case, you’ve made new ones) and that you’d like the changes to be stored as a migration.
Migrations are how Django stores changes to your models (and thus your database schema) - they’re just files on disk. You can read the migration for your new model if you like; it’s the file polls/migrations/0001_initial.py.
Under Version Control, after you push the migrations file, for example, 0001_initial.py. Other developers just pull the file then run
python manage.py sqlmigrate your_app 0001 # to see what happen
python manage.py migrate your_app 0001
More about the Version Control:
Version control
Because migrations are stored in version control, you’ll occasionally come across situations where you and another developer have both committed a migration to the same app at the same time, resulting in two migrations with the same number.
Don’t worry - the numbers are just there for developers’ reference, Django just cares that each migration has a different name. Migrations specify which other migrations they depend on - including earlier migrations in the same app - in the file, so it’s possible to detect when there’s two new migrations for the same app that aren’t ordered.
When this happens, Django will prompt you and give you some options. If it thinks it’s safe enough, it will offer to automatically linearize the two migrations for you. If not, you’ll have to go in and modify the migrations yourself - don’t worry, this isn’t difficult, and is explained more in Migration files below.
I have a few projects with lots of South migrations, including ones that contain a fair amount of custom SQL that need to be run in a specific order. After upgrading to Django 1.7, this is the recommendation on how to convert a project to use South (from the Django documentation):
If you already have pre-existing migrations created with South, then the upgrade process to use django.db.migrations is quite simple:
Ensure all installs are fully up-to-date with their migrations.
Remove 'south' from INSTALLED_APPS.
Delete all your (numbered) migration files, but not the directory or __init__.py - make sure you remove the .pyc files too.
Run python manage.py makemigrations. Django should see the empty migration directories and make new initial migrations in the new format.
Run python manage.py migrate. Django will see that the tables for the initial migrations already exist and mark them as applied without running them.
In short, "wipe your existing migrations and Django will take care of the rest".
What is not mentioned here is what to do when existing South migrations don't only consist of model changes, but instead contain direct SQL, data migrations, etc, that need to be run in order. In this case, the auto-generated Django migrations will miss a lot of things, since not all of these changes are obvious from introspecting a models file.
Ideally, one would be able to run the existing migrations using South, and then have Django migrations take over. What might be the best way to go about this? If this is not possible or very much not recommended, what is the best alternative?
Maybe this post can help you. Essentially you have to:
Change your current migration directory from 'migrations' to 'south_migrations'
Update your settings with this line
SOUTH_MIGRATION_MODULES = {
'your_app': 'your_project.your_app.south_migrations',
}