Оптимизация sql запросов

# User@Host: XXX @ localhost []
# Thread_id:XXX  Schema: XXXX
# Query_time: 2.562369  Lock_time: 0.000282  Rows_sent: 0  Rows_examined: 43572  Rows_affected: 0  Rows_read: 680
SELECT u.email, u.title, u.url, u.location, u.use_avatar, u.signature, u.email_setting, u.num_posts, u.registered, u.admin_note, SUM(r.rep_plus) AS count_rep_plus, SUM(r.rep_minus) AS count_rep_minus, u.reputation_enable, p.id, p.poster AS username, p.poster_id, p.poster_ip, p.poster_email, p.message, p.hide_smilies, p.posted, p.edited, p.edited_by, g.g_id, g.g_user_title, o.user_id AS is_online FROM posts AS p INNER JOIN users AS u ON u.id=p.poster_id INNER JOIN groups AS g ON g.g_id=u.group_id LEFT JOIN online AS o ON (o.user_id=u.id AND o.user_id!=1 AND o.idle=0) LEFT JOIN reputation as r ON (r.user_id=u.id) WHERE p.topic_id=105 GROUP BY p.id ORDER BY p.id LIMIT 670,10;