protected function load_event_records($start = 0) {
        global $DB;
        while ($records = $DB->get_records_select(
            'event',
            'id <> :parentid AND repeatid = :repeatid',
            [
                'parentid' => $this->parentid,
                'repeatid' => $this->parentid,
            ],
            'id ASC',
            '*',
            $start,
            self::DB_QUERY_LIMIT
        )) {
            yield $records;
            $start += self::DB_QUERY_LIMIT;
        }
    }