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# Schema Revisions and Migrations

Schema revisions and migrations is a serious issue when you develop a application beyond a certain scale.

there is no functionallity in Camelot as such for handling this ‘automagically’.

The recommended approach is to use sqlalchemy-migrate http://code.google.com/p/sqlalchemy-migrate/ It requires a bit of an effort to set it up and understand it, but once you got it up and running, it’s well worth the effort.

There are 2 approaches, depending on the needs of your project :

## Leave it all to sqlalchemy-migrate

Let sqla-migrate do a diff between your model and your db and add tables / columns as needed. This is easy to implement, but not very powerfull and will fail on complex migrations.

## Use schema revisions

Work with database revisions (takes some work to get up and running, but very nice), you can even create database views and update those views as well, and migrate data to the next schema revision etc.

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