Nomad is a simple migration application, which specifically takes into account properties of development with DVCS and is completely agnostic from ORM or whatever you are using to access your database. It uses simple SQL scripts to migrate and can run pre- and post-processing routines written in any language (Python, Ruby or whatever do you use for your application).
Nomad's migration store is a directory with nomad.ini and a other directories inside. Each directory in it containing migration.ini is a single migration and name of child directory is an identifier of migration.
It looks like this:
migrations/ nomad.ini 2011-11-11-first-migration/ migration.ini up.sql 2011-11-12-second-migration/ migration.ini 1-pre.py 2-up.sql 3-post.py
- There is no downgrades - nobody ever tests them, they are rarely necessary
- You can write migration in whatever language you want, tool only helps you track applied migrations and dependencies
- .sql is treated differently and executed against database, configured in nomad.ini
- Only .sql and executable files are executed. You can put READMEs, pieces of documentation, whatever you want alongside your migrations.
- Name matters - everything is executed in order. Order is determined by using human sort (so that x-1.sql is earlier than x-10.sql, you can always check sorting with ls --sort=version).