My previous post focused on some of the problems of doing multi-tenant MySQL.

One of the reasons why I started hacking on Drizzle was that the multi-tenancy options for MySQL just weren’t very good (this is also the reason why I run my blog in a VM and not a shared hosting solution).

What you really want is to be able to give your users access to a virtual database server. What you don’t want is to be administering a separate database server for each of your users. What you want are CATALOGs.

A CATALOG is a collection of SCHEMAs (which have TABLEs in them). Each CATALOG is isolated from all the others. Once you connect to a catalog, that’s it. They are entirely separate units. There are no cross-catalog queries or CHANGE CATALOG commands. It is as if each catalog is its own database server.