public static function backup_includes_file_references($backupid) {
        global $CFG, $DB;

        $sql = "SELECT count(r.repositoryid)
                  FROM {files} f
                  LEFT JOIN {files_reference} r
                       ON r.id = f.referencefileid
                  JOIN {backup_ids_temp} bi
                       ON f.id = bi.itemid
                 WHERE bi.backupid = ?
                       AND bi.itemname = 'filefinal'";
        $count = $DB->count_records_sql($sql, array($backupid));
        return (int)(bool)$count;
    }