protected function fill_forum_cache($forumids) {
        global $DB;

        $requiredfields = [
                'id',
                'course',
                'forcesubscribe',
                'type',
            ];
        list($in, $params) = $DB->get_in_or_equal($forumids);
        $this->forums = $DB->get_records_select('forum', "id $in", $params, '', implode(', ', $requiredfields));
        foreach ($this->forums as $id => $forum) {
            \mod_forum\subscriptions::fill_subscription_cache($id);
            \mod_forum\subscriptions::fill_discussion_subscription_cache($id);
        }
    }