fix

blog/mysq-advance/index.md

@@ -36,4 +36,4 @@ MySQL 运维篇
 - 3. [https://www.yuque.com/heychu/akbndd/zhuxqd](https://www.yuque.com/heychu/akbndd/zhuxqd)
 
 
-https://www.bilibili.com/video/BV1Kr4y1i7ru?p=90&spm_id_from=pageDriver
+https://www.bilibili.com/video/BV1Kr4y1i7ru?p=92&spm_id_from=pageDriver
\ No newline at end of file

blog/mysq-advance/sql-optimization.md

@@ -205,3 +205,252 @@ mysql> select count(*) from tb_user;
 
 ```
 
+## 2、主键优化
+
+### 2.1、数据组织方式
+
+在InnoDB存储引擎中，表数据都是根据主键顺序组织存放的，
+
+这种存储方式的表称为`索引组织表`（index organized table IOT）
+
+![](img/mysql-b+tree.png)
+
+![](img/innodb-store.png)
+
+
+### 2.2、页分裂
+
+页可以为空，也可以填充一半，也可以填充100%。
+
+每个页包含了2-N行数据（如果一行数据太大，会行溢出），根据主键排列
+
+如果插入的数据主键不是顺序的，有可能发生页分裂
+
+![](img/page-split-1.png)
+
+![](img/page-split-2.png)
+
+### 2.3、页合并
+
+当删除一行记录的时候，实际上记录并没有被物理删除，只是记录被标记（flaged）为删除。
+
+并且它的空间变得允许被其他记录声明使用。
+
+当页中删除的记录达到 MERGE_THRESHOLD (默认为页的50%)，
+
+InnoDB会开始寻找最靠近的页（前或后）看看是否可以将两个页合并优化空间使用。
+
+MERGE_THRESHOLD ： 合并也的阈值，可以自己设置，在创建表或者创建索引时指定
+
+![](img/page-merge-1.png)
+
+![](img/page-merge-2.png)
+
+### 2.4、主键设计原则
+
+1. 满足业务需求的情况下，尽量降低主键的长度（二级索引叶子节点存放主键，主键过长会占用大量磁盘空间）
+
+2. 插入数据时，尽量选择顺序插入，选择使用 `auto_increment` 自增主键（不是顺序插入，会造成页分裂）
+
+3. 尽量不要使用UUID做主键或者是其他自然主键，如身份证号（长度较长，耗费磁盘io）
+
+4. 业务操作时，避免对主键的修改
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+## 3、order by 优化
+
+- using filesort：通过表的索引或全表扫描，读取满足条件的数据行，然后在`排序缓冲区sort buffer`中完成排序操作，所有不是通过索引直接返回排序结果的排序都叫FileSort排序
+
+- using index: 通过有序索引顺序扫描直接返回有序数据，这种情况即为using index,不需要额外排序，操作效率高
+
+
+测试数据
+
+```sql
+-- 查看表数据
+mysql> select * from tb_user limit 3;
++----+-----------+-------------+---------------------+------+--------+----------------+
+| id | name      | phone       | profession          | age  | status | email          |
++----+-----------+-------------+---------------------+------+--------+----------------+
+|  1 | 费阳      | 13777763170 | 法务经理            |   27 |      1 | wyao@gmail.com |
+|  2 | 祁海燕    | 13400806360 | 日式厨师            |   23 |      0 | jwan@jin.cn    |
+|  3 | 姬秀英    | 18281241586 | 食品/饮料研发       |   29 |      0 | li97@wang.cn   |
++----+-----------+-------------+---------------------+------+--------+----------------+
+3 rows in set (0.01 sec)
+
+-- 查看索引
+mysql> show index from tb_user;
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| Table   | Non_unique | Key_name                       | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| tb_user |          0 | PRIMARY                        |            1 | id          | A         |        9804 |     NULL |   NULL |      | BTREE      |         |               | YES     | NULL       |
+| tb_user |          0 | idx_user_phone                 |            1 | phone       | A         |        9804 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          0 | idx_user_phone_name            |            1 | phone       | A         |        9804 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          0 | idx_user_phone_name            |            2 | name        | A         |        9804 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_name                  |            1 | name        | A         |        9130 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            1 | profession  | A         |         948 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            2 | age         | A         |        6232 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            3 | status      | A         |        7596 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_email_5                    |            1 | email       | A         |        3955 |        5 |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+9 rows in set (0.03 sec)
+
+-- 删除索引
+drop index idx_user_phone on tb_user;
+
+drop index idx_user_phone_name on tb_user;
+
+drop index idx_user_name on tb_user;
+
+show index from tb_user;
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| Table   | Non_unique | Key_name                       | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| tb_user |          0 | PRIMARY                        |            1 | id          | A         |        9804 |     NULL |   NULL |      | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            1 | profession  | A         |         948 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            2 | age         | A         |        6232 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            3 | status      | A         |        7596 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_email_5                    |            1 | email       | A         |        3955 |        5 |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+5 rows in set (0.00 sec)
+```
+
+索引测试
+
+```sql
+-- 没有创建索引时，根据age, phone进行排序 Using filesort 
+mysql> explain select id, age, phone from tb_user order by age, phone;
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra          |
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+|  1 | SIMPLE      | tb_user | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 9804 |   100.00 | Using filesort |
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+1 row in set, 1 warning (0.00 sec)
+
+-- 创建索引
+create index idx_user_age_phone on tb_user(age, phone);
+
+-- 创建索引后，根据age进行升序排序
+mysql> explain select id, age, phone from tb_user order by age;
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                | key_len | ref  | rows | filtered | Extra       |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone | 52      | NULL | 9804 |   100.00 | Using index |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+1 row in set, 1 warning (0.00 sec)
+
+-- 创建索引后，根据age, phone进行升序排序
+mysql> explain select id, age, phone from tb_user order by age, phone;
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                | key_len | ref  | rows | filtered | Extra       |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone | 52      | NULL | 9804 |   100.00 | Using index |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-------------+
+1 row in set, 1 warning (0.01 sec)
+
+-- 创建索引后，根据age, phone进行降序排序
+mysql> explain select id, age, phone from tb_user order by age desc, phone desc;
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+----------------------------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                | key_len | ref  | rows | filtered | Extra                            |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+----------------------------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone | 52      | NULL | 9804 |   100.00 | Backward index scan; Using index |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+----------------------------------+
+1 row in set, 1 warning (0.00 sec)
+
+-- 交换age，phone的先后位置 出现Using filesort
+mysql> explain select id, age, phone from tb_user order by phone, age;
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                | key_len | ref  | rows | filtered | Extra                       |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone | 52      | NULL | 9804 |   100.00 | Using index; Using filesort |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+1 row in set, 1 warning (0.01 sec)
+
+-- age升序排列，phone降序排列，出现Using filesort
+mysql> explain select id, age, phone from tb_user order by age asc, phone desc;
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                | key_len | ref  | rows | filtered | Extra                       |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone | 52      | NULL | 9804 |   100.00 | Using index; Using filesort |
++----+-------------+---------+------------+-------+---------------+--------------------+---------+------+------+----------+-----------------------------+
+1 row in set, 1 warning (0.00 sec)
+
+-- 创建age升序，phone降序的索引
+create index idx_user_age_phone_ad on tb_user(age asc, phone desc);
+
+-- 查看索引 （Collation： A=asc, D=desc）
+mysql> show index from tb_user;
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| Table   | Non_unique | Key_name                       | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+| tb_user |          0 | PRIMARY                        |            1 | id          | A         |        9804 |     NULL |   NULL |      | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            1 | profession  | A         |         948 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            2 | age         | A         |        6232 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_profession_age_status |            3 | status      | A         |        7596 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_email_5                    |            1 | email       | A         |        3955 |        5 |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_age_phone             |            1 | age         | A         |          11 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_age_phone             |            2 | phone       | A         |        9804 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_age_phone_ad          |            1 | age         | A         |          11 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+| tb_user |          1 | idx_user_age_phone_ad          |            2 | phone       | D         |        9804 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
++---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
+9 rows in set (0.02 sec)
+
+-- 创建索引后，age升序排列，phone降序排列
+mysql> explain select id, age, phone from tb_user order by age asc, phone desc;
++----+-------------+---------+------------+-------+---------------+-----------------------+---------+------+------+----------+-------------+
+| id | select_type | table   | partitions | type  | possible_keys | key                   | key_len | ref  | rows | filtered | Extra       |
++----+-------------+---------+------------+-------+---------------+-----------------------+---------+------+------+----------+-------------+
+|  1 | SIMPLE      | tb_user | NULL       | index | NULL          | idx_user_age_phone_ad | 52      | NULL | 9804 |   100.00 | Using index |
++----+-------------+---------+------------+-------+---------------+-----------------------+---------+------+------+----------+-------------+
+1 row in set, 1 warning (0.00 sec)
+
+
+-- 如果没有用到覆盖索引，会出现：Using filesort
+mysql> explain select * from tb_user order by age asc, phone desc;
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra          |
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+|  1 | SIMPLE      | tb_user | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 9804 |   100.00 | Using filesort |
++----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+----------------+
+1 row in set, 1 warning (0.00 sec)
+```
+
+### 3.1、优化原则
+
+1. 根据排序字段建立合适的索引，多字段排序时，也遵循最左前缀法则
+
+2. 尽量使用覆盖索引
+
+3. 多字段排序，一个升序一个降序，此时需要注意联合索引在创建时的规则（asc/desc）
+
+4. 如果不可避免的出现filesort, 大数据量排序时，可以适当增大排序缓冲区的大小 sort_buffer_size(默认值256k)
+
+```sql
+mysql> show variables like 'sort_buffer_size';
++------------------+--------+
+| Variable_name    | Value  |
++------------------+--------+
+| sort_buffer_size | 262144 |
++------------------+--------+
+1 row in set (0.03 sec)
+```