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: alan@blogometer.com

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.