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 (
  key1 int,
  col1 int,
  filler1 char(32),
  key(key1)
);

insert into t10 select 
  A.a + 1000*B.a,
  MOD(A.a + 1000*B.a, 10000),
  'filler-data'
from 
  one_k A, one_k B;

set use_stat_tables=preferably;
set histogram_size=100;
set optimizer_use_condition_selectivity=4;
analyze table t10 persistent for all;

explain extended select * from t10 where col1=1000111 order by key1 desc limit 10 ;
+------+-------------+-------+-------+---------------+------+---------+------+------+----------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+------+----------+-------------+
|    1 | SIMPLE      | t10   | index | NULL          | key1 | 5       | NULL |   10 |   100.00 | Using where |
+------+-------------+-------+-------+---------------+------+---------+------+------+----------+-------------+

MariaDB [j12]> explain extended select * from t10 where col1=1000111;
+------+-------------+-------+------+---------------+------+---------+------+---------+----------+-------------+
| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows    | filtered | Extra       |
+------+-------------+-------+------+---------------+------+---------+------+---------+----------+-------------+
|    1 | SIMPLE      | t10   | ALL  | NULL          | NULL | NULL    | NULL | 1000000 |     0.00 | Using where |
+------+-------------+-------+------+---------------+------+---------+------+---------+----------+-------------+