Options: Avoid unnecessary DB calls when updating network options.

Adds a `maybe_serialize()` comparison for the old and new values in `update_network_option()` to avoid unnecessary database writes when options contain identical objects.

Props bor0.
Fixes #44956.


Built from https://develop.svn.wordpress.org/trunk@44662


git-svn-id: http://core.svn.wordpress.org/trunk@44493 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/option.php

@@ -1583,7 +1583,16 @@ function update_network_option( $network_id, $option, $value ) {
 	 */
 	$value = apply_filters( "pre_update_site_option_{$option}", $value, $old_value, $option, $network_id );
 
-	if ( $value === $old_value ) {
+	/*
+	 * If the new and old values are the same, no need to update.
+	 *
+	 * Unserialized values will be adequate in most cases. If the unserialized
+	 * data differs, the (maybe) serialized data is checked to avoid
+	 * unnecessary database calls for otherwise identical object instances.
+	 *
+	 * See https://core.trac.wordpress.org/ticket/44956
+	 */
+	if ( $value === $old_value || maybe_serialize( $value ) === maybe_serialize( $old_value ) ) {
 		return false;
 	}