public function update_moved(context $newparent) {
        global $DB;

        $frompath = $this->_path;
        $newpath  = $newparent->path . '/' . $this->_id;

        $trans = $DB->start_delegated_transaction();

        $setdepth = '';
        if (($newparent->depth +1) != $this->_depth) {
            $diff = $newparent->depth - $this->_depth + 1;
            $setdepth = ", depth = depth + $diff";
        }
        $sql = "UPDATE {context}
                   SET path = ?
                       $setdepth
                 WHERE id = ?";
        $params = array($newpath, $this->_id);
        $DB->execute($sql, $params);

        $this->_path  = $newpath;
        $this->_depth = $newparent->depth + 1;

        $sql = "UPDATE {context}
                   SET path = ".$DB->sql_concat("?", $DB->sql_substr("path", strlen($frompath)+1))."
                       $setdepth
                 WHERE path LIKE ?";
        $params = array($newpath, "{$frompath}/%");
        $DB->execute($sql, $params);

        $this->mark_dirty();

        context::reset_caches();

        $trans->allow_commit();
    }