Mysql nepoužívá index v dotazech s offsety

Zvažte následující, kde vnucuji 2,2 milionu řádků do tabulky

Schéma

create table tbl
(   id int auto_increment primary key,
    thing int not null
)engine=MyISAM;

insert tbl(thing) values (7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7),(7);

insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;
insert into tbl(thing) select thing from tbl;

Počítání

select count(*) as theCount,max(id) as theMax,min(id) as thMin from tbl;
+----------+---------+-------+
| theCount | theMax  | thMin |
+----------+---------+-------+
|  2228224 | 2228224 |     1 |
+----------+---------+-------+

Dotaz A (váš, používá odvozenou tabulku)

explain 
SELECT *  
FROM `tbl` 
JOIN 
(SELECT id FROM `tbl` ORDER BY id LIMIT 1000000, 100) as b 
on `b`.`id` = `tbl`.`id`;
+----+-------------+------------+--------+---------------+---------+---------+------+---------+-------------+
| id | select_type | table      | type   | possible_keys | key     | key_len | ref  | rows    | Extra       |
+----+-------------+------------+--------+---------------+---------+---------+------+---------+-------------+
|  1 | PRIMARY     | <derived2> | ALL    | NULL          | NULL    | NULL    | NULL | 1000100 | NULL        |
|  1 | PRIMARY     | tbl        | eq_ref | PRIMARY       | PRIMARY | 4       | b.id |       1 | NULL        |
|  2 | DERIVED     | tbl        | index  | NULL          | PRIMARY | 4       | NULL | 2228224 | Using index |
+----+-------------+------------+--------+---------------+---------+---------+------+---------+-------------+

Dotaz B (nikoli odvozená tabulka)

explain 
SELECT t1.*  
FROM tbl t1 
JOIN tbl t2 
on t2.id = t1.id 
where t2.id>1000000 
limit 100 
+----+-------------+-------+--------+---------------+---------+---------+--------------------+---------+--------------------------+
| id | select_type | table | type   | possible_keys | key     | key_len | ref                | rows    | Extra                    |
+----+-------------+-------+--------+---------------+---------+---------+--------------------+---------+--------------------------+
|  1 | SIMPLE      | t2    | range  | PRIMARY       | PRIMARY | 4       | NULL               | 1195836 | Using where; Using index |
|  1 | SIMPLE      | t1    | eq_ref | PRIMARY       | PRIMARY | 4       | so_gibberish.t2.id |       1 | NULL                     |
+----+-------------+-------+--------+---------------+---------+---------+--------------------+---------+--------------------------+

Pro ty, kteří nejsou obeznámeni s používáním Explain , podívejte se na zápis, který jsem udělal zde