foreach ($filter_values as $id => $filter_value) {
				$total = $filter_value["total"];
				if (!strlen($total)) {
					$list_id = $filter_value["list_id"];
					$where = $filter_value["where"];
					if (!$where) {
						$where = $filter_where_sql;
					}
					$where = str_replace("{value_id}", $list_id, $where);
					$where = str_replace("{table_value}", $list_id, $where);
					$sql  = get_filter_sql1($filter_type, $filter_from_sql, $filter_join_sql, $where, "", $show_sub_products, $category_path);
					if ($sql && $where) {
						$sql = $sql.' LIMIT 1';
						$total = get_db_value($sql);
					}
				}

				if ($total) {
				//	$filter_values[$id]["total"] = $total;
				} else {
					unset($filter_values[$id]);
				}
			}

SELECT DISTINCT `size` FROM /* таблица или группа таблиц */ WHERE /* тут параметры фильтра товаров, для которых надо взять размеры  */