ADDENDUM

Ordered database schema migrations.

Home: http://bigeasy.github.com/addendum

Source: http://github.com/bigeasy/addendum/tree/master
Documentation: http://wiki.github.com/bigeasy/addendum

Issues and Tasks: http://bigeasy.lighthouseapp.com/projects/28792

Contact: [email protected]

MOTIVATION

Addendum was written after I was tripped up by automatic schema updates via JPA and Hiberate. The automatic updates were not magic enough to implement all of the changes I wanted to see in my underlying schema.

Additionally, there was a time when changes to file system directory structures accompanied a schema update. I wanted to run some Java code to shuffle the files, based on the changes to the schema.

Automatic building of schemas by Hibernate created more problems than it solved. Addendum builds a database from a bootstrap point, adding changes one after another.

Assuming a linear progression of changes, updates and not merges, you can deploy an application and have it patch the schema from where ever it last left off, or you can deploy an application for the first time, and have it build a database by applying patches from zero.

Addendum delegates DDL to a dialect library that will generate SQL DDL based on a domain-specific language. You use the DSL to describe the tables that back the object in your application using either Java types or abstracted SQL types. The dialect will map your type definitions to the specific SQL type definitions of the underlying database.

LIMITATIONS

Unlike Ruby on Rails migrations, Addendum provides no facility for undoing an addendum. That adds a lot of code for something that never really works. If you want to be able to reset the database to a previous state, make sure to create a backup using the backup facilities of RDMS.

There are helper methods for generating SQL in the DSL, but they do not ensure the type safety of the SQL statements. Addendum will not trap the use of the DSL to generate an insert statement to populate an SQL NUMBER column with a 'Hello, World!' string.