Search user in wordpress sidewide (at least at backend and if you use wp user query any where ) for user's display name , if you are here you know why I used this filter

gistfile1.txt

add_filter('user_search_columns', 'user_search_columns_bd' , 10, 3);

function user_search_columns_bd($search_columns, $search, $this){
	//if(!in_array($search_columns, 'display_name')){
	if(!in_array('display_name', $search_columns)){
		$search_columns[] = 'display_name';
	}
	return $search_columns;
}