upgradation error : ci:2

[eluser]krishnakumar2k[/eluser]
when i upgrader one of my ci project 1.7 to 2 am getting this error
Fatal error: Call to undefined method CI_DB_mysql_driver::where() in D:\wamp\www\frame_ci2\system\libraries\Session.php on line 200

my active records are enabled.

[eluser]InsiteFX[/eluser]
Show your code!

InsiteFX