Redmine

it's not enought. You need define in your environnement.rb a
config :

config.action_controller.session_store = :active_record_store

if you not use this configuration you don't use this session
store in your database.

Maybe made a rake file which create and apply this migration
is better. Because you need delete it after. If you don't delete
it you can be problem with the future migration.