Database schema upgrades can be inefficient with lots of database tables because of maybe_create_table() function
|Reported by:||jamescollins||Owned by:|
The maybe_create_table() function in wp-admin/includes/upgrade.php performs a SHOW TABLES query (which returns every table in the database) then loops over all of these to see if a the specified table exists.
WPMU was recently modified to optimise this, and donncha has suggested that this fix be implemented in WP as well.
(See WPMU Trac Ticket #833 for more information)