Error Reading from Database when one uses Ratings with Discussion Forum

Error reading from database

More information about this error

Debug info: ORA-00979: not a GROUP BY expression
SELECT r.itemid, r.component, r.ratingarea, r.contextid,
SUM(r.rating) AS aggrrating, COUNT(r.rating) AS numratings,
ur.id, ur.userid, ur.scaleid, ur.rating AS usersrating
FROM m_rating r
LEFT JOIN m_rating ur ON ur.contextid = r.contextid AND
ur.itemid = r.itemid AND
ur.component = r.component AND
ur.ratingarea = r.ratingarea AND
ur.userid = :o_userid
WHERE r.contextid = :o_contextid AND
r.itemid = :o_param9 AND
r.component = :o_component AND
r.ratingarea = :o_ratingarea
GROUP BY r.itemid, r.component, r.ratingarea, r.contextid, ur.id, ur.userid, ur.scaleid
ORDER BY r.itemid
[array (
'o_userid' => '77',
'o_contextid' => '162',
'o_param9' => '34',
'o_component' => 'mod_forum',
'o_ratingarea' => 'post',
)]
Stack trace:
line 393 of /lib/dml/moodle_database.php: dml_read_exception thrown
line 268 of /lib/dml/oci_native_moodle_database.php: call to moodle_database->query_end()
line 1070 of /lib/dml/oci_native_moodle_database.php: call to oci_native_moodle_database->query_end()
line 585 of /rating/lib.php: call to oci_native_moodle_database->get_records_sql()
line 5469 of /mod/forum/lib.php: call to rating_manager->get_ratings()
line 271 of /mod/forum/discuss.php: call to forum_print_discussion()