请注意，这并不是建议您过一会儿再使用MyISAM。我只用它来获取我的ID，最小，最大和计数。因此，请忽略引擎。
create table ratings( id int auto_increment primary key, thing int null)engine=MyISAM;insert ratings (thing) values (null),(null),(null),(null),(null),(null),(null),(null),(null);insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;insert ratings (thing) select thing from ratings;
我现在有470万行
select count(*),min(id),max(id) from ratings;+----------+---------+---------+| count(*) | min(id) | max(id) |+----------+---------+---------+| 4718592 | 1 | 4718592 |+----------+---------+---------+select * from `ratings` order by id limit 499500, 500;-- 1 second on a dumpy laptop
。
explain select * from `ratings` order by id limit 499500, 500;+----+-------------+---------+------+---------------+------+---------+------+---------+----------------+| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |+----+-------------+---------+------+---------------+------+---------+------+---------+----------------+| 1 | SIMPLE | ratings | ALL | NULL | NULL | NULL | NULL | 4718592 | Using filesort |+----+-------------+---------+------+---------------+------+---------+------+---------+----------------+
。
explain select * from `ratings` where id>=499501 limit 500;+----+-------------+---------+-------+---------------+---------+---------+------+---------+-----------------------+| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |+----+-------------+---------+-------+---------------+---------+---------+------+---------+-----------------------+| 1 | SIMPLE | ratings | range | PRIMARY | PRIMARY | 4 | NULL | 4198581 | Using index condition |+----+-------------+---------+-------+---------------+---------+---------+------+---------+-----------------------+
故事的寓意可能是使用where子句。
不能排除出现僵局的可能性。
