Database migrations

For the production version, using tools such as spring.jpa.hibernate.ddl-auto=update is not recommended. Instead, database migration tools such as Liquibase or Flyway should be used. For qc-atlas we have chosen the former.

Workflow

• Edit your Hibernate mapped classes as needed (add and remove classes and attributes)
• Run mvn compile && mvn liquibase:diffChangeLog
• Manually check that the new changelog/yyyy-MM-dd-hh-mm.xml does what you expect, edit it if it does not (for details on how to do that, see the Changelogs section)
• Run mvn liquibase:update to update your target database's schema (during development, this is done automatically when starting the backend)
• Repeat

The default database credentials are stored in the root pom.xml at db.url etc. You can override these using Maven profiles.

Changelogs

Liquibase uses a changelog to list all changes, in order, made to your database. To implement complex changes (for example, migrating data), these changelogs need to be written/updated manually. The following resources help with that:

• Changelog format overview
• Grouped changes (changesets)
• Change types

All changelogs are stored in the org.planqk.atlas.core module at src/main/resources/db/changes/.

Limitations

• Right now, column type changes are ignored by the automatic diff generation tool (see GH). These changes need to be recorded manually.