From f158620eabb48e94d55447951e7d61e2c9575a1f Mon Sep 17 00:00:00 2001
From: Jonny Harris <spacedmonkey@git.wordpress.org>
Date: Tue, 20 Sep 2022 14:24:08 +0000
Subject: [PATCH] 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.

git-svn-id: https://develop.svn.wordpress.org/trunk@54256 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-admin/includes/schema.php                | 10 ++++++++++
 src/wp-includes/class-wp-network.php            |  5 ++---
 tests/phpunit/tests/multisite/getMainSiteId.php | 11 +++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/wp-admin/includes/schema.php b/src/wp-admin/includes/schema.php
index c8bc92e44c..57ffe69054 100644
--- a/src/wp-admin/includes/schema.php
+++ b/src/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 {
diff --git a/src/wp-includes/class-wp-network.php b/src/wp-includes/class-wp-network.php
index 75b407e541..fd92c5ba70 100644
--- a/src/wp-includes/class-wp-network.php
+++ b/src/wp-includes/class-wp-network.php
@@ -255,9 +255,8 @@ class WP_Network {
 		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 @@ class WP_Network {
 				);
 				$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 );
 			}
 		}
 
diff --git a/tests/phpunit/tests/multisite/getMainSiteId.php b/tests/phpunit/tests/multisite/getMainSiteId.php
index 3a6e9c4d8c..f68c5409e7 100644
--- a/tests/phpunit/tests/multisite/getMainSiteId.php
+++ b/tests/phpunit/tests/multisite/getMainSiteId.php
@@ -88,6 +88,17 @@ if ( is_multisite() ) :
 			$this->assertSame( $main_site_id, $result );
 		}
 
+		/**
+		 * @ticket 55802
+		 */
+		public function test_get_main_site_id_with_different_network_cache_id() {
+			$this->assertSame( self::$site_ids['wordpress.org/'], get_main_site_id( self::$network_ids['wordpress.org/'] ), 'Main blog id needs to match blog id of wordpress.org/' );
+			$this->assertSame( self::$site_ids['wordpress.org/'], (int) get_network_option( self::$network_ids['wordpress.org/'], 'main_site' ), 'Network option needs to match blog id of wordpress.org/' );
+
+			$this->assertSame( 0, get_main_site_id( self::$network_ids['wp.org/'] ), 'Main blog id should not be found' );
+			$this->assertSame( 0, (int) get_network_option( self::$network_ids['wp.org/'], 'main_site' ), 'Network option should not be found' );
+		}
+
 		/**
 		 * @ticket 29684
 		 */