Database schema changes

Kallithea uses Alembic for :ref:`database migrations <upgrade_db>` (upgrades and downgrades).

If you are developing a Kallithea feature that requires database schema changes, you should make a matching Alembic database migration script:

1. :ref:`Create a Kallithea configuration and database <setup>` for testing the migration script, or use existing development.ini setup.

   Ensure that this database is up to date with the latest database schema before the changes you're currently developing. (Do not create the database while your new schema changes are applied.)

2. Create a separate throwaway configuration for iterating on the actual database changes:

   kallithea-cli config-create temp.ini
   

   Edit the file to change database settings. SQLite is typically fine, but make sure to change the path to e.g. temp.db, to avoid clobbering any existing database file.

3. Make your code changes (including database schema changes in db.py).

4. After every database schema change, recreate the throwaway database to test the changes:

   rm temp.db
   kallithea-cli db-create -c temp.ini --repos=/var/repos --user=doe --email doe@example.com --password=123456 --no-public-access --force-yes
   kallithea-cli repo-scan -c temp.ini
   

5. Once satisfied with the schema changes, auto-generate a draft Alembic script using the development database that has not been upgraded. (The generated script will upgrade the database to match the code.)

   alembic -c development.ini revision -m "area: add cool feature" --autogenerate
   

6. Edit the script to clean it up and fix any problems.

   Note that for changes that simply add columns, it may be appropriate to not remove them in the downgrade script (and instead do nothing), to avoid the loss of data. Unknown columns will simply be ignored by Kallithea versions predating your changes.

7. Run alembic -c development.ini upgrade head to apply changes to the (non-throwaway) database, and test the upgrade script. Also test downgrades.

   The included development.ini has full SQL logging enabled. If you're using another configuration file, you may want to enable it by setting level = DEBUG in section [handler_console_sql].

The Alembic migration script should be committed in the same revision as the database schema (db.py) changes.

See the Alembic documentation for more information, in particular the tutorial and the section about auto-generating migration scripts.