I wish I could work on these magical projects that people with blogs work on, in which everything works like it's supposed to do. In my experience, though, it's not unusual to be forced by management to migrate to a new RDBMS a year into a project. The last time it happened to me, we were using Rails and had very little difficulty migrating from PostgreSQL to MySQL. We didn't need to alter application code or rewrite tests and only had to manage config changes and migrate the data. I imagine the transition wouldn't be much different if we had been using Django.
