Question about active_record_store

I am not understanding the behavior of session storage with

In environment.rb, I uncommented
config.action_controller.session_store = :active_record_store

I have this line in a controller (that does get executed)
session[:user_id] =

I would think that this should store something in the database. But the
session table is empty:
x_development=# select * from sessions;
id | session_id | data | updated_at
(0 rows)

The data seems to be stored somewhere…I’m just not sure where. Any

Never mind. I needed to restart the server after making the change in