I spent most of the last post talking about magic, but what I intended to talk about is the regular occurrence of the database getting out of sync with the domain objects in Grails.

In theory, based on using the Update directive in the database configuration, my database should be updated to match the domain objects. In my experience, however, Grails regularly fails to properly upgrade the database, and I’m forced to delete the whole thing in order to get the system sane again. This doesn’t happen all the time - generally only when I need to create a new relationship between tables or apply a new constraint (for example, allowing a column/field to be null).

Luckily, since I’m using Hypersonic SQL, this is straightforward. Shut down your grails app, and from your grails project top-level directory:

cd db
rm devDb.*      # or whatever the name of your database is

Then restart grails. It will regenerate the database (without data) with the latest constraints and structures you’ve made. You’ll need to repopulate, but there are tools for that.