Networks and Sites: Store main site id of a network in network options.

Instead of caching main site id an object cache, store main site id on a network options. This results in less database queries on sites without persistent object caching. 

Props spacedmonkey, johnjamesjacoby, peterwilsoncc, desrosj.
Fixes #55802.
Built from https://develop.svn.wordpress.org/trunk@54256


git-svn-id: http://core.svn.wordpress.org/trunk@53815 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/schema.php

@@ -1068,6 +1068,16 @@ function populate_network( $network_id = 1, $domain = '', $email = '', $site_nam
 		update_user_meta( $site_user->ID, 'source_domain', $domain );
 		update_user_meta( $site_user->ID, 'primary_blog', $current_site->blog_id );
 
+		// Unable to use update_network_option() while populating the network.
+		$wpdb->insert(
+			$wpdb->sitemeta,
+			array(
+				'site_id'    => $network_id,
+				'meta_key'   => 'main_site',
+				'meta_value' => $current_site->blog_id,
+			)
+		);
+
 		if ( $subdomain_install ) {
 			$wp_rewrite->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
 		} else {

wp-includes/class-wp-network.php

@@ -255,9 +255,8 @@ private function get_main_site_id() {
 		if ( $site->domain === $this->domain && $site->path === $this->path ) {
 			$main_site_id = (int) $site->id;
 		} else {
-			$cache_key = 'network:' . $this->id . ':main_site';
 
-			$main_site_id = wp_cache_get( $cache_key, 'site-options' );
+			$main_site_id = get_network_option( $this->id, 'main_site' );
 			if ( false === $main_site_id ) {
 				$_sites       = get_sites(
 					array(
@@ -270,7 +269,7 @@ private function get_main_site_id() {
 				);
 				$main_site_id = ! empty( $_sites ) ? array_shift( $_sites ) : 0;
 
-				wp_cache_add( $cache_key, $main_site_id, 'site-options' );
+				update_network_option( $this->id, 'main_site', $main_site_id );
 			}
 		}
 

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-54255';
+$wp_version = '6.1-alpha-54256';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.