Heroku plugin and db:migrate

Using the Heroku plugin, I can push my project to Heroku.  I've set up a Run Configuration and security config and everything pushes fine and my app launches.  However, even whilst setting it up I was wondering how I get it to run a db:migrate to set up the database.  In the end I thought that maybe it just runs that automatically.  Obviously it doesn't because although my app will successfully launch it pretty much fails immediately because there is no conigured DB.  I know how to run this stuff from the command line but it feels like it should be something that runs as part of using the plugin.  There are some configurable tasks on the Run Configuration dialog that includes the possibility of setting up a Rake task but the help implies that these are run before the Run Configuration is launched but, in any case, trying to add one fails so it's sort of moot.

How do I get the plugin to run rake db:migrate after pushing to Heroku?

thanks