[wp-trac] [WordPress Trac] #46388: WP_User::get_data_by(): Cache non-existent users to prevent triggering multiple queries

[WordPress Trac]

#46388: WP_User::get_data_by(): Cache non-existent users to prevent triggering
multiple queries
-------------------------+-----------------------------
 Reporter:  Asgaros      |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Cache API    |    Version:  trunk
 Severity:  normal       |   Keywords:  has-patch
  Focuses:  performance  |
-------------------------+-----------------------------
 Assume you use the WP_User::get_data_by() function to get the main user
 fields queried against an ID:

 {{{
 WP_User::get_data_by('ID', 1337);
 }}}

 If you call this function multiple times - by calling the function
 directly or indirectly by using functions like get_userdata or get_avatar
 - and an user with the given ID does not exist, the database-query is
 getting executed multiple times resulting in duplicate queries:

 {{{
 SELECT * FROM wp_users WHERE ID = '1337'
 }}}

 To prevent triggering multiple queries, non-existing users should get
 stored inside the WP Object Cache similar as in the get_option() function
 for non-existing options.

 The attached patch checks if the user ID exists in the WP Object Cache
 inside of the notusers-array so the WP_User::get_data_by() function
 returns FALSE if this is the case:

 {{{
 // Prevent non-existent users from triggering multiple queries
 $notusers = wp_cache_get( 'notusers', 'users' );
 if ( isset( $notusers[ $user_id ] ) ) {
         return false;
 }
 }}}

 If the user is not existent in the notusers-array but he also does not
 exist inside of the database, the user gets added to the WP Object Cache
 before the WP_User:get_data_by() function returns FALSE:

 {{{
 // User does not exist, so we must cache its non-existence
 if ( ! is_array( $notusers ) ) {
         $notusers = array();
 }

 $notusers[ $user_id ] = true;
 wp_cache_set( 'notusers', $notusers, 'users' );
 }}}

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/46388>
WordPress Trac <https://core.trac.wordpress.org/>
WordPress publishing platform