create table ten(a int);

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

create table one_k(a int);

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

create table t10 (a int, b int, c int, key(a,b));

insert into t10 select a,a,a from one_k;

explain select * from t10 force index(a) where a between 10 and 20 and b+1 <3333 order by a desc, b desc;

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

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

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

|  1 | SIMPLE      | t10   | NULL       | range | a             | a    | 5       | NULL |    1 |   100.00 | Using index condition; Backward index scan |

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

mysql> explain select * from t10 force index(a) where a=10 and b+1 <3333 order by a desc, b desc;

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

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

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

|  1 | SIMPLE      | t10   | NULL       | ref  | a             | a    | 5       | const |    1 |   100.00 | Using where; Backward index scan |

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

mysql> explain select * from t10 force index(a) where a=10 and b+1 <3333 order by a asc, b asc;

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

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

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

|  1 | SIMPLE      | t10   | NULL       | ref  | a             | a    | 5       | const |    1 |   100.00 | Using index condition |

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

1 row in set, 1 warning (0.01 sec)

void QEP_TAB::push_index_cond(const JOIN_TAB *join_tab, uint keyno,

                              Opt_trace_object *trace_obj) {

  JOIN *const join_ = join();

  DBUG_TRACE;

  ASSERT_BEST_REF_IN_JOIN_ORDER(join_);

  assert(join_tab == join_->best_ref[idx()]);

  if (join_tab->reversed_access)  // @todo: historical limitation, lift it!

    return;