wp_posts query problem

Hey guys!

our “wp_posts” has over 15k entries and slows down our whole wordpress installation (up to two minutes sometimes), cause one query blocks all other queries on the “wp_posts” table.

Maybe a LIMIT will fix this issue, but unfortunately I don’t have any idea where to finde the where. Can anyone help?

Query (founded via phpMyAdmin):

SELECT ID , post_author , post_date , post_date_gmt , post_status , post_name , post_modified , post_modified_gmt , post_parent , post_type
FROM wp_posts
WHERE (
(
post_status = ‘publish’
AND (
post_type = ‘post’
OR post_type = ”
)
)
OR (
post_status = ‘publish’
AND post_type = ‘page’
)
)
AND post_password = ”
ORDER BY post_modified DESC

THX for any help in advance.

Cheers
Whooper