Wordpress mysqld insane CPU usage

Question

What is wrong with this query that causes MySQL cpu usage to spike? The cpu usage is like this until the db runs out of memory.

$sql = "SELECT c.* 
    FROM   hatt_postmeta a 
           inner join hatt_postmeta b 
                   ON a .post_id = b .post_id 
           inner join hatt_postmeta c 
                   ON a .post_id = c .post_id 
    WHERE  ( a .meta_key = 'ht_size_width' 
             AND a .meta_value = 165 ) 
           AND ( b .meta_key = 'ht_size_ratio' 
                 AND b .meta_value = 70 ) 
           AND c .meta_key = 'ht_size_diameter' 
    GROUP  BY c .meta_value 
    ORDER  BY c .meta_value ASC";

$result= $wpdb->get_results( $sql );

Update: every query is getting 100% cpu usage

Answer 1

I've fixed this by deleting orphaned terms. Orphans can cause poor SQL performance, so you can install some plugin to clean it out for you. Below is a list of plugins that you can use. Hope this helps.

http://www.wpoptimus.com/611/wordpress-plugins-cleanup-optimize-database-improve-performance