Newbie difficulty using south with pycharm – DatabaseError: no such table: south_migrationhistory

djangodjango-southpycharm

I'm using sqlite3 and pycharm to learn more about django, and googled to find that south is recommended to make it easier to modify models after they have been created.

I'm trying to follow the advice on http://south.aeracode.org/docs/tutorial/part1.html#starting-off.

The most success I've had so far is to create a simple model and run syncdb before adding south to installed_apps. That way the intial tables are created and I get a chance to create a super user. (Django admin seems to fret if there are no users).

Then I add south to installed_apps, and run django_manage.py schemamigration bookmarks –initial

It seems to work fine. A new directory is created called migrations with a couple of files in it in my app folder and an encouraging message.
"Created 0001_initial.py. You can now apply this migration with: ./manage.py migrate bookmarks"

The next step – django_manage.py" migrate bookmarks generates the following error message
django.db.utils.DatabaseError: no such table: south_migrationhistory.

I thought that table would be created in the first schememigration step. What am I missing? Can anyone help?

Marg

Best Answer

South uses a table if its own to keep track of which migrations have been applied. Before you can apply any migrations, this must have been created, using python ./manage.py syncdb.

As well as for setting up south, you will find syncdb sometimes necessary for non-south apps in your project, such as the very common django.contrib.auth.

Note that as a convenience, you can run both in one go like this

python ./manage.py syncdb --migrate

Related Solutions

What’s the recommended approach to resetting migration history using Django South

If you need to selectively (for just one app) reset migrations that are taking too long, this worked for me.

rm <app-dir>/migrations/*
python manage.py schemamigration <app-name> --initial
python manage.py migrate <app-name> 0001 --fake  --delete-ghost-migrations

Don't forget to manually restore any dependencies on other apps by adding lines like depends_on = (("<other_app_name>", "0001_initial"),("<yet_another_app_name>", "0001_initial")) to your <app-dir>/migrations/0001_initial.py file, as the first attribute in your migration class just below class Migration(SchemaMigration):.

You can then ./manage.py migrate <app-name> --fake --delete-ghost-migrations on other environments, per this SO answer. Of course if you fake the delete or fake the migrate zero you'll need to manually delete any left-over db tables with a migration like this.

A more nuclear option is to ./manage.py migrate --fake --delete-ghost-migrations on the live deployment server followed by a [my]sqldump. Then pipe that dump into [my]sql on the environments where you need the migrated, fully-populated db. South sacrilege, I know, but worked for me.

Python – Why don’t the south migrations work

South allows you to create migrations when you first start out with a new app and the tables haven't been added to the database yet, as well as creating migrations for legacy apps that already have tables in the database. The key is to know when to do what.

Your first mistake was when you deleted your migrations, as soon as you did that, and then ran syncdb, Django didn't know that you wanted south to manage that app anymore, so it created the tables for you. When you created your initial migrations and then ran migrate, south was trying to create tables that django already created, and thus your error.

At this point you have two options.

Delete the tables for the wall app from your database and then run $ py manage.py migrate wall This will run the migration and create your tables.
Fake out the initial migration run $ py manage.py migrate wall 0001 --fake This will tell south that you already have the tables on the database so just fake it, which will add a row to the south_migrationhistory table, so that the next time you run a migrate it will know that the first migration has already been run.

Setting up a brand new project and no database

create your database
add south to installed apps
run syncdb, this will add the django and south tables to the database
add your apps
for each app run python manage.py schemamigration app_name --initial this will create the initial migration files for your app
then run south migrate python manage.py migrate app_name this will add the tables to the database.

Setting up a legacy project and database

add south to installed apps
run syncdb, this will add the south tables to the database
for each of your apps run python manage.py schemamigration app_name --initial This will create your initial migrations
for each of your apps run python manage.py migrate app_name 0001 --fake , this will fake out south, it won't do anything to the database for those models, it will just add records to the south_migrationhistory table so that the next time you want to create a migration, you are all set.

Setting up a legacy project and no database

create database
add south to installed apps
for each of your apps run python manage.py schemamigration app_name --initial This will create your initial migrations
run syncdb, this will add any apps that don't have migrations to the database.
then run south migrate python manage.py migrate this will run all migrations for your apps.

Now that you are setup with south, you can start using south to manage model changes to those apps. The most common command to run is python manage.py schemamigration app_name migration_name --auto that will look at the last migration you ran and it will find the changes and build out a migration file for you. Then you just need to run python manage.py migrate and it alter your database for you.

Hope that helps.