too much sorting

Hi when we update 5-6 wordpress post simultanously cpu load goes high and site stops working. When i asked to my server admin he replied that this is cause of too much sorting. here what he replied

there is some query using that table in queries;

it can use index or somekind of tuning

example
| 18454 | india | localhost | blog | Query | 0 | Copying to tmp table | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_postmeta ON (wp_posts.ID = wp_p |
| 18455 | india | localhost | blog | Query | 0 | Copying to tmp table | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_postmeta ON (wp_posts.ID = wp_p |
| 18456 | india | localhost | blog | Sleep | 0 | | NULL

as you can seee, it is joining wp_posts and wp_postmeta
it is trying to create virtual table out of it

creating indexes with those columns will reduce weight of query