MySQL Forums :: Performance :: Long execution time despite LIMIT 3

It somehow seems I might be getting there:


I could rewrite the SELECT as follows:

(SELECT m.*, m.flags + 0 flags
FROM messages_test m
WHERE (m.thread = 817549.001266066) AND (id_user_s = 817549) AND (del_s = 0))

UNION

(SELECT m.*, m.flags + 0 flags
FROM messages_test m
WHERE (m.thread = 817549.001266066) AND (id_user_r = 817549) AND (del_r = 0))

order by id desc
LIMIT 3;


and have indexes like:
test1 (thread,id_user_r,del_r)
test2 (thread,id_user_s,del_s)


What do you think?