Multisite improvements in WordPress 6.1

Using the metadata API for network options

The way that network options are accessed is changing in WordPress 6.1. Network options have always been stored in a meta table called sitemeta. This name is confusing, as “site” in this context means “network,” not to be confused with blog meta, used to store site metadata. Prior to WordPress 6.1, the functions get_network_option, add_network_option, update_network_options, and delete_network_option used custom database queries and caching. This resulted in some performance issues and lots of code to maintain.

In WordPress 6.1, the network options functions have been updated to use the more established metadata API, which is already used for metadata of other object types like posts, terms, and users. This effectively makes a function like get_network_option a wrapper around get_metadata. This has a number of advantages including:

• Consistency with other metadata types
• Support for register_meta functionality, such as default values
• Improved cache priming
• Fewer database queries, as all network options are primed in a single request

Along with these improvements, WP_Network_Query has a new parameter called update_network_meta_cache that allows for all networks in the query to prime the network options in a single query. 

One side effect of this change is that newly updated network options using an integer value may result in a string being returned. When using values like this with an integer comparison, it is important to allow cast to an int. In the old implementation, the second page load of the option would have resulted in returning a string. This change can be considered a fix but it is different from the current behavior. 

This change makes cache group site-options no longer in use and a candidate to be removed in future releases. 

For more information, visit Trac ticket #37181. 

Store main site ID of network in network options

When a multisite is created in WordPress 6.1, the main site ID on the network is stored in network options. As the main site on the network does not change in most cases, this is a value that can be stored for future reference. This saves a call to WP_Site_Query to look up the main site by domain and path in the bootstrap process which makes This lookup wasteful and not needed. This change also helps setup multiple networks, as noted above, since network options are primed in a single request. This means that when looking up multiple networks, the main site ID is now primed in along with other network options, resulting in fewer database queries / cache lookups. 

For more information, visit Trac ticket #55802. 

Thanks to @flixos90 and @milana_cap for peer review, and @shetheliving and @webcommsat for proofreading.

#6-1, #core-multisite, #dev-notes, #dev-notes-6-1, #multisite, #performance