Delete related entries

Sorry, the link got lost. See here:
http://wordpress.stackexchange.com/questions/23522/wordpress-site-causing-lots-of-server-io

term_relationships and postmeta entries are also deleted.

DELETE a,b,c
FROM wp_posts a
LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id)
LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
WHERE a.post_type = 'revision'

By the way, I tired switching off the multi-user option in your plugin and it was not saved – it was ticked again when I reloaded the page. (WordPress 3.5.1, Buddypress 1.6.4)