public static function migrate($file_id, $test_key=false)
    {
        global $CFG, $PDOX;

        $retval = false;

        // Check to see where we are moving to...
        if ( isset($CFG->dataroot) && strlen($CFG->dataroot) > 0 ) {
            if ( ! $test_key ) {
                $retval = self::blob2file($file_id);
            }
        } else {
            $retval = self::blob2blob($file_id);
        }
        return $retval;
    }