Schema Migrations in TurboGears with Migrate
Posted by Tim Freund Mon, 06 Aug 2007 00:42:00 GMT
I learned about the importance of schema migrations the hard way. At my previous job, I helped a team upgrade a Java web application. The upgrade involved schema changes, and I had the forethought to script the upgrade and thoroughly test it on the development database. Even with that preparation, the night of the upgrade would teach me two important questions that new developers should always ask of their team. Does the development database schema match the production database schema? And do you know how to restore the database from backups should anything go wrong? The answers to both questions on that night were no and oh no. Sometime after midnight things started working.
A better way existed. I first learned of schema migrations a few months earlier when exposed to ActiveRecord::Migrations. After using them on several projects, I was itching to have the same capability in my Python and Java projects. The Pythonic answer came in the form of Migrate, a schema migration library for SQLAlchemy, and direct support for TurboGears was added with TGMigrate. Having migrate integrated with my projects greatly reduces my blood pressure on deployment days. Of course, I still make sure that my database backups are working.
Those interested in integrating Migrate with a TurboGears project might enjoy the screencast I just completed on the topic. If you use SQLAlchemy but avoid Migrate, I would be interested to hear what is holding you back.
Schema refactoring and migration was one of three topics at the last DotNext Kansas City Tech Coffee meeting. Notes on the schema migration talk were posted to Squidoo.
My apologies to those with small screens. I will record my next screencast in a smaller window. Your comments on today's screencast are appreciated.
