I just ran into a related problem upgrading to 2.3.0. I carefully stepped through the whole upgrade process, though I was puzzled that, at the conclusion of running the upgrade script, I was prompted to run the upgrade script. It wouldn’t run again, though, so I deleted the upgrade folder. Then, though the admin section was fine, no public pages could load. I turned on full verbosity in “Output and Debugging Preferences,” and got this error:
A Database Error Occurred
Error Number: 1054
Unknown column 'site_id' in 'where clause'
SELECT `member_id`, `admin_sess`, `last_activity` FROM (`exp_sessions`) WHERE `session_id` = '62a37320bd7e0b80bd47c4510edfbd2d52cdda8a' AND `ip_address` = '137.54.140.169' AND `user_agent` = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.202 Safari/535.1' AND `site_id` = 1
Filename: libraries/Session.php
Line Number: 708
I quickly altered exp_sessions and added a site_id column (making it of type “text,” figuring that’d cover everything), and the site worked immediately. (So, what should the data type be for that field?)
So, count this as another report of broken-ness pertaining to the site_id column in exp_sessions.