Detailed explanation of the reasons and optimization methods for excessive offset affecting performance during mysql query

CREATE TABLE `member` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(10) NOT NULL COMMENT '姓名', `gender` tinyint(3) unsigned NOT NULL COMMENT '性别', PRIMARY KEY (`id`), KEY `gender` (`gender`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

<?php
$pdo = new PDO("mysql:host=localhost;dbname=user","root",&#39;&#39;);for($i=0; $i<1000000; $i++){    $name = substr(md5(time().mt_rand(000,999)),0,10);    $gender = mt_rand(1,2);    $sqlstr = "insert into member(name,gender) values(&#39;".$name."&#39;,&#39;".$gender."&#39;)";    $stmt = $pdo->prepare($sqlstr);    $stmt->execute();}
?>mysql> select count(*) from member;
+----------+| count(*) |
+----------+|  1000000 |
+----------+1 row in set (0.23 sec)

mysql> select version();
+-----------+| version() |
+-----------+| 5.6.24    |
+-----------+1 row in set (0.01 sec)

mysql> select * from member where gender=1 limit 10,1;
+----+------------+--------+| id | name       | gender |
+----+------------+--------+| 26 | 509e279687 |      1 |
+----+------------+--------+1 row in set (0.00 sec)mysql> select * from member where gender=1 limit 100,1;
+-----+------------+--------+| id  | name       | gender |
+-----+------------+--------+| 211 | 07c4cbca3a |      1 |
+-----+------------+--------+1 row in set (0.00 sec)mysql> select * from member where gender=1 limit 1000,1;
+------+------------+--------+| id   | name       | gender |
+------+------------+--------+| 1975 | e95b8b6ca1 |      1 |
+------+------------+--------+1 row in set (0.00 sec)

mysql> select * from member where gender=1 limit 100000,1;
+--------+------------+--------+| id     | name       | gender |
+--------+------------+--------+| 199798 | 540db8c5bc |      1 |
+--------+------------+--------+1 row in set (0.12 sec)mysql> select * from member where gender=1 limit 200000,1;
+--------+------------+--------+| id     | name       | gender |
+--------+------------+--------+| 399649 | 0b21fec4c6 |      1 |
+--------+------------+--------+1 row in set (0.23 sec)mysql> select * from member where gender=1 limit 300000,1;
+--------+------------+--------+| id     | name       | gender |
+--------+------------+--------+| 599465 | f48375bdb8 |      1 |
+--------+------------+--------+1 row in set (0.31 sec)

select * from member where gender=1 limit 300000,1;

mysql> select id from member where gender=1 limit 300000,1;
+--------+| id     |
+--------+| 599465 |
+--------+1 row in set (0.09 sec)

mysql> select index_name,count(*) from information_schema.INNODB_BUFFER_PAGE where INDEX_NAME in('primary','gender') and TABLE_NAME like '%member%' group by index_name;
Empty set (0.04 sec)

mysql> select * from member where gender=1 limit 300000,1;
+--------+------------+--------+| id     | name       | gender |
+--------+------------+--------+| 599465 | f48375bdb8 |      1 |
+--------+------------+--------+1 row in set (0.38 sec)mysql> select index_name,count(*) from information_schema.INNODB_BUFFER_PAGE where INDEX_NAME in('primary','gender') and TABLE_NAME like '%member%' group by index_name;
+------------+----------+| index_name | count(*) |
+------------+----------+| gender     |      261 || PRIMARY    |     1385 |
+------------+----------+2 rows in set (0.06 sec)

mysql> select id from member where gender=1 limit 300000,1;
+--------+| id     |
+--------+| 599465 |
+--------+1 row in set (0.08 sec)mysql> select index_name,count(*) from information_schema.INNODB_BUFFER_PAGE where INDEX_NAME in('primary','gender') and TABLE_NAME like '%member%' group by index_name;
+------------+----------+| index_name | count(*) |
+------------+----------+| gender     |      263 || PRIMARY    |       13 |
+------------+----------+2 rows in set (0.04 sec)

mysql> select a.* from member as a inner join (select id from member where gender=1 limit 300000,1) as b on a.id=b.id;
+--------+------------+--------+| id     | name       | gender |
+--------+------------+--------+| 599465 | f48375bdb8 |      1 |
+--------+------------+--------+1 row in set (0.08 sec)