What are the possible values of the Hibernate hbm2ddl.auto configuration and what do they do
From the community documentation:
hibernate.hbm2ddl.auto Automatically validates or exports schema DDL to the database when the SessionFactory is created. With create-drop, the database schema will be dropped when the SessionFactory is closed explicitly.
e.g. validate | update | create | create-drop
So the list of possible options are,
- validate: validate the schema, makes no changes to the database.
- update: update the schema.
- create: creates the schema, destroying previous data.
- create-drop: drop the schema when the SessionFactory is closed explicitly, typically when the application is stopped.
- none: does nothing with the schema, makes no changes to the database
These options seem intended to be developers tools and not to facilitate any production level databases, you may want to have a look at the following question; Hibernate: hbm2ddl.auto=update in production?
The configuration property is called hibernate.hbm2ddl.auto
In our development environment we set hibernate.hbm2ddl.auto=create-drop to drop and create a clean database each time we deploy, so that our database is in a known state.
In theory, you can set hibernate.hbm2ddl.auto=update to update your database with changes to your model, but I would not trust that on a production database. An earlier version of the documentation said that this was experimental, at least; I do not know the current status.
Therefore, for our production database, do not set hibernate.hbm2ddl.auto - the default is to make no database changes. Instead, we manually create an SQL DDL update script that applies changes from one version to the next.