diff --git a/htdocs/holiday/card_group.php b/htdocs/holiday/card_group.php
index b63a3ae657b..5e571f077c8 100644
--- a/htdocs/holiday/card_group.php
+++ b/htdocs/holiday/card_group.php
@@ -261,6 +261,7 @@ if (empty($reshook)) {
 			if (!$error) {
 				$TusersToProcess = array();
 				// usergroup  select
+				// better perf on single sql
 				/** GROUPS */
 				$sql = ' SELECT DISTINCT u.rowid,u.lastname,u.firstname from ' . MAIN_DB_PREFIX . 'user as  u';
 				$sql .= ' LEFT JOIN  ' . MAIN_DB_PREFIX . 'usergroup_user as ug on ug.fk_user = u.rowid  ';