How to save the user_id in a separate column when using ActiveRecord::SessionStore?

Hi!

I'm converting my Rails 3.1 app from cookie sessions to database
sessions.
I've added an extra column on the sessions table to save the user_id.

I read the documentation in
http://apidock.com/rails/v3.1.0/ActiveRecord/SessionStore and googled
but can't seem to find a way to set the session's user_id that works.

Can someone help?

Thanks

As a work around I'm now saving user_id and session_id's in a separate
table. I couln't find a way to write to the sessions table!