How do you manage schema upgrades to a production database?
In general my rule is: "The application should manage it's own schema."
This means schema upgrade scripts are part of any upgrade package for the application and run automatically when the application starts. In case of errors the application fails to start and the upgrade script transaction is not committed. The downside to this is that the application has to have full modification access to the schema (this annoys DBAs).
I've had great success using Hibernates SchemaUpdate feature to manage the table structures. Leaving the upgrade scripts to only handle actual data initialization and occasional removing of columns (SchemaUpdate doesn't do that).
Regarding testing, since the upgrades are part of the application, testing them becomes part of the test cycle for the application.
Afterthought: Taking on board some of the criticism in other posts here, note the rule says "it's own". It only really applies where the application owns the schema as is generally the case with software sold as a product. If your software is sharing a database with other software, use other methods.
Liquibase
liquibase.org:
- it understands hibernate definitions.
- it generates better schema update sql than hibernate
- it logs which upgrades have been made to a database
- it handles two-step changes (i.e. delete a column "foo" and then rename a different column to "foo")
- it handles the concept of conditional upgrades
- the developer actually listens to the community (with hibernate if you are not in the "in" crowd or a newbie -- you are basically ignored.)
http://www.liquibase.org
opinion
the application should never handle a schema update. This is a disaster waiting to happen. Data outlasts the applications and as soon as multiple applications try to work with the same data ( the production app + a reporting app for example) -- chances are they will both use the same underlying company libraries... and then both programs decide to do their own db upgrade ... have fun with that mess.
I am a big fan of Red Gate products that help creating SQL packages to update database schemas. The database scripts can be added to source control to help with versioning and rollback.