Optimizer trace: lots of join_execution elements produced for correlated subquery

create table ten(a int primary key);

insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

create table one_k(a int primary key);

insert into one_k select A.a + B.a* 10 + C.a * 100 from ten A, ten B, ten C;

explain

select * from one_k where a > 1000 + (select max(a) from ten where ten.a<one_k.a);

+------+--------------------+-------+------+---------------+------+---------+------+------+-------------+

| id   | select_type        | table | type | possible_keys | key  | key_len | ref  | rows | Extra       |

+------+--------------------+-------+------+---------------+------+---------+------+------+-------------+

|    1 | PRIMARY            | one_k | ALL  | NULL          | NULL | NULL    | NULL | 1000 | Using where |

|    2 | DEPENDENT SUBQUERY | ten   | ALL  | NULL          | NULL | NULL    | NULL | 10   | Using where |

+------+--------------------+-------+------+---------------+------+---------+------+------+-------------+

set optimizer_trace=1;

select * from one_k where a > 1000 + (select max(a) from ten where ten.a<one_k.a);

select * from information_schema.optimizer_trace\G

            "join_execution": {

              "select_id": 2,

              "steps": []

            }

            "join_execution": {

              "select_id": 2,

              "steps": []

            }

            "join_execution": {

              "select_id": 2,

              "steps": []

            }

            "join_execution": {

              "select_id": 2,

              "steps": []

            }