Derby, the Cauldron and Java DB
Apache Derby project is the cauldron where Sun starts the forging of Java DB, Sun's distribution of Derby and the premier Java database in the world!
Most recently, Knut Anders Hatlen, Java DB engineering and committer to the Apache Derby project, has been writing about the new features being shipped in Java DB 10.5.
It is important to know that Java DB is a project 3 years in the making, and we're now witnessing people interested in installing this database in hundreds of instances, in the middle tier of their applications. Java DB is particularly unique because it can easily be embedded with a Java application in a JVM. (Anyone who has studied Java somewhat closely should already be completely familiar with this fact.)
You can review the derby-users list on Apache to discover the level of sophistication in the user community, or go to the derby-dev list on Apache to discover and contribute to recent ideas and development with Derby replication.
In one of his many Derby 10.5 preview blog entries, Knut describes the use of generated columns, and follows up on their usability in a particular example involving case-insensitive search.