feat: replace post meta sync storage with dedicated sync_updates table

Author: josephfusco

src/wp-admin/includes/schema.php

@@ -186,6 +186,14 @@ function wp_get_db_schema( $scope = 'all', $blog_id = null ) {
 	KEY post_parent (post_parent),
 	KEY post_author (post_author),
 	KEY type_status_author (post_type,post_status,post_author)
+) $charset_collate;
+CREATE TABLE $wpdb->sync_updates (
+	id bigint(20) unsigned NOT NULL auto_increment,
+	room_hash char(32) NOT NULL,
+	update_value longtext NOT NULL,
+	created_at datetime NOT NULL default '0000-00-00 00:00:00',
+	PRIMARY KEY  (id),
+	KEY room_hash (room_hash,id)
 ) $charset_collate;\n";
 
 	// Single site users table. The multisite flavor of the users table is handled below.

src/wp-admin/includes/upgrade.php

@@ -886,7 +886,7 @@ function upgrade_all() {
 		upgrade_682();
 	}
 
-	if ( $wp_current_db_version < 61644 ) {
+	if ( $wp_current_db_version < 61697 ) {
 		upgrade_700();
 	}
 
@@ -2508,6 +2508,16 @@ function upgrade_700() {
 			)
 		);
 	}
+
+	// Clean up orphaned wp_sync_storage posts from the beta1 post-meta storage approach.
+	if ( $wp_current_db_version < 61697 ) {
+		$wpdb->delete( $wpdb->postmeta, array( 'meta_key' => 'wp_sync_update' ) );
+		$wpdb->delete( $wpdb->postmeta, array( 'meta_key' => 'wp_sync_awareness' ) );
+		$wpdb->delete(
+			$wpdb->posts,
+			array( 'post_type' => 'wp_sync_storage' )
+		);
+	}
 }
 
 /**

src/wp-includes/class-wpdb.php

@@ -299,6 +299,7 @@ class wpdb {
 		'term_relationships',
 		'termmeta',
 		'commentmeta',
+		'sync_updates',
 	);
 
 	/**
@@ -404,6 +405,15 @@ class wpdb {
 	 */
 	public $posts;
 
+	/**
+	 * WordPress Sync Updates table.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @var string
+	 */
+	public $sync_updates;
+
 	/**
 	 * WordPress Terms table.
 	 *