slow query

gistfile1.txt

SELECT u.id
              FROM mdl_user u
              JOIN (SELECT DISTINCT eu1_u.id
              FROM mdl_user eu1_u
            JOIN mdl_role_assignments eu1_ra3 ON (eu1_ra3.userid = eu1_u.id AND eu1_ra3.roleid IN (5) AND eu1_ra3.contextid IN (1,236,15,152))
JOIN mdl_user_enrolments eu1_ue ON eu1_ue.userid = eu1_u.id
JOIN mdl_enrol eu1_e ON (eu1_e.id = eu1_ue.enrolid AND eu1_e.courseid = $1)
           WHERE eu1_u.deleted = 0 AND eu1_u.id <> $2 AND eu1_ue.status = $3 AND eu1_e.status = $4 AND eu1_ue.timestart < $5 AND (eu1_ue.timeend = 0 OR eu1_ue.timeend > $6)) je ON je.id = u.id
             WHERE u.deleted = 0 ORDER BY u.lastname, u.firstname, u.id