About this document

A quick explanation about database versioning in Leosac.

Introduction

Database version is a complicated tasks. We rely on our Object Relational Mapper, ODB, to provide infrastructure to support database versioning.

ODB maintains a changelog of the database structure. This changelog is committed in the repository and is required to properly track change and support automatic database migration.

ODB comes with per-schema versioning, which allows use to make use of powerful versioning strategy.

Leosac Database Schemas

ODB comes with per-schema versioning. This means the same database can have multiple versions at the same.

Leosac makes use of this, by defining multiple schemas:

The core schema is managed by the core Leosac program. It includes Users, Groups, Credentials, and a lot of user object.
It's the main schema, and can only evolves between Leosac release.
Each module that is database-aware must define and use its own schema. A module should name its schema module-MODULE_NAME.
The version of module's schema can change between module release. It is the responsibility of the module developer to properly version his module.

At the code level

The database.hpp uses a pragma db model version(x, y) so that we can define Leosac's core schema version.

It is important for module code to define ODB_NO_BASE_VERSION before including any file that could include database.hpp. Defining ODB_NO_BASE_VERSION will prevent the use of pragma db model version(x, y) and will allows module code to pick it's own version.