Learning by doing

Google has donated Hibernate Shards - a Java 5 add-on to Hibernate that allows application driven data partitioning with your custom or their pre-build configurations. One thing that caught my eye was that when they covered partitioned Native ID generation (aka Identity), they mentioned having Database A use a range 0-200000, Database B use range 200001 - 400000, etc. I know that MySQL cluster suggests using something like this: Database A: Starting ID 1, Increment ID by 3 (number of databases) Database B: Starting ID 2, Increment ID by 3 Database C: Starting ID 3, Increment ID by 3 This allows a hands-off approach, and easily lets you divide ID by 3 and use the remainder to map to a "Shard". Of course, if your data changes significantly, you may have to dump and reload to add another database. One way to avoid a dump and reload is to pick an increment that is larger than your actual database count, and just drop an extra database in an the available Starting ID. This ...