Extend `models/db.php` and switch to a more object oriented pattern. Tables should be objects; then we can do:

    $usersTable->getField( 'cookievalue' )->changeTypeTo( 'TEXT CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL

Where `$usersTable = $db->getTableByName( 'users' )`, `getField` returns a field object, and `db` is a database object.