How to store "custom session data" in sessions table?

[eluser]inktri[/eluser]
So I'm using the session class and want to store in the sessions table more than just the IP, session id, etc. How can I store the custom session data such as username, and logged_in in the sessions table? I tried altering the schema so each sessions record has a username field and a logged_in field; however the values of those fields never change accordingly.

Code:

$newdata = array(
                   'username'  => 'johndoe',
                   'email'     => '[email protected]',
                   'logged_in' => TRUE
               );

$this->session->set_userdata($newdata);