Users: Call `add_user_meta()` instead of `update_user_meta()` when adding metadata to a new user.

This improves the performance of inserting users as it removes one unnecessary `SELECT` query for every row of metadata inserted.

Props swissspidy, spacedmonkey, johnbillion

Fixes #59212

Built from https://develop.svn.wordpress.org/trunk@56478


git-svn-id: http://core.svn.wordpress.org/trunk@55990 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/user.php

@@ -2431,9 +2431,16 @@ function wp_insert_user( $userdata ) {
 
 	$meta = array_merge( $meta, $custom_meta );
 
-	// Update user meta.
-	foreach ( $meta as $key => $value ) {
-		update_user_meta( $user_id, $key, $value );
+	if ( $update ) {
+		// Update user meta.
+		foreach ( $meta as $key => $value ) {
+			update_user_meta( $user_id, $key, $value );
+		}
+	} else {
+		// Add user meta.
+		foreach ( $meta as $key => $value ) {
+			add_user_meta( $user_id, $key, $value );
+		}
 	}
 
 	foreach ( wp_get_user_contact_methods( $user ) as $key => $value ) {

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56477';
+$wp_version = '6.4-alpha-56478';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.