spatial index(geo)とindex(geo) using rtreeの違い

point.sql

create table point(
    id bigint not null auto_increment primary key,
    spa geometry not null,
    rtr geometry not null,
    spatial index(spa),
    index(rtr) using rtree
) engine=InnoDB, default charset=utf8mb4;

result

mysql> show create table point¥G

Create Table: CREATE TABLE `point` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `spa` geometry NOT NULL,
  `rtr` geometry NOT NULL,
  PRIMARY KEY (`id`),
  SPATIAL KEY `spa` (`spa`),
  SPATIAL KEY `rtr` (`rtr`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci