Main point is that you:
- save your current database tables structure
- change your model tables
- scan for differences and create script
- then write changes to your database with automatically generated python script.
Sound's simple? I't not all so simple in fact. App that you need to learn is Django-south. Its main objectives are to provide a simple, stable and database-independent migration layer to prevent all the hassle schema changes over time bring to your Django applications. It has quite understandable tutorial here.
So if you're tired of ALTER'ing your tables and writing code to python Sqlite console or editing raw SQL, go get yourself a copy of south. It's an app that IMHO everybody should use/hear/understand.
It is meant to change old one and quite simple command 'manage.py syncdb' someday. For now go get yourself this tool and learn to use it. It took me about half an hour to understand basics.. So it's not hard (at first) :).
Brief look at usage:
1. Install app in some way. Use pip/easy_install script or simply put 'south' dir to your project root dir.
Add 'south', to your INSTALLED_APPS dictionary.
!IMPORTANT! you need to make syncdb after that. Another way wo will get an error with future commands.
2. Connect existing app's to migrations. Use command python manage.py convert_to_south myapp to convert your app from syncdb ready to south migratable. Or you can run python manage.py schemamigration newappname --initial to add south migrations ability to your new app. In general it will create directory 'migrations' inside your app directory.
3. Change your model. I dont think you need separate stop here. But... Just in case add some field to your django model like bollean or text and/or edit your existing field rather by adding 'null=True' for e.g.
4. Create your migration. It can be done by command python manage.py schemamigration newappname --auto to create your migration script. you can check it in your app's 'migrations' dir. It has numbers in the beginning with migration number.
5. Run your migration. It is done by command python manage.py migrate appname or even without an app name: python manage.py migrate to migrate all apps. Thats it.
Hope you'll never use 'syncdb' again for complex tasks like this. I'm adding it to my base developer tools. And you?
How is that different from the manual?
ReplyDeleteIt's a bit why do you need it and shorten a bit...
ReplyDeleteHi
ReplyDeleteI am using South but I am getting an error while running syncdb. 'no module named southregistration'. I have installed south using pip for python 2.7. and I have included south in INSTALLED_APP as well but still I am getting this error
If Django doesn’t seem to pick this up, check that you’re not overriding INSTALLED_APPS elsewhere, and that you can run import south from inside ./manage.py shell with no errors.
DeletePlease run the console from where you manage.py lives (environment if you're using virtualenv) and try to do:
(virtualenv_name):projectdir username$ python
Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import south
>>>
IF you see any errors there then you've probably have not installed south... try to do:
easy_install South
It tells you what to do. Database has the table named like so. Try renaming your model (resulting to different name of that table to migrate to) and either delete your destination table in the database. Other way you can not use south in case this has happened without really creating of that table before and entirely by south-migrations. It means you may have to have other database backend in order south to support migrations. E.g. more new MySQL or whatever you are using there as a database backend.
ReplyDelete@Yordis - you can also use "--fake" for the initial migration if you are adding this to a legacy database that already has the initial sync'd tables in it. This means you don't have to drop everything.
ReplyDeleteHello i install south with : $pip install south
ReplyDeleteall was correct. I put 'south', in INSTALLED_APPS .
But when i'm running $python manage.py syncdb
I got this error :
There is no South database module 'south.db.sqlite3' for your database. Please either choose a supported database, check for SOUTH_DATABASE_ADAPTER[S] settings, or remove South from INSTALLED_APPS.
You need to check your settings.py especially for DATABASES section. Checking for typical novice mistakes like forgotten comma or something similar may also be a case here. Note you need to syncdb before installing south to your apps section. This will create an actual database first...
Delete