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blog/mysq-advance/index.md
浏览文件 @ 517683aa
......@@ -25,13 +25,13 @@
MySQL 运维篇
## 其他网友的笔记
## 网友笔记
- [https://dhc.pythonanywhere.com/entry/share/?key=3ad29aad765a2b98b2b2a745d71bef715507ee9db8adbec98257bac0ad84cbe4](https://dhc.pythonanywhere.com/entry/share/?key=3ad29aad765a2b98b2b2a745d71bef715507ee9db8adbec98257bac0ad84cbe4)
- 1. [https://dhc.pythonanywhere.com/entry/share/?key=3ad29aad765a2b98b2b2a745d71bef715507ee9db8adbec98257bac0ad84cbe4](https://dhc.pythonanywhere.com/entry/share/?key=3ad29aad765a2b98b2b2a745d71bef715507ee9db8adbec98257bac0ad84cbe4)
- [https://aismy.github.io/2021/08/17/MYSQL/](https://aismy.github.io/2021/08/17/MYSQL/)
- 2. [https://aismy.github.io/2021/08/17/MYSQL/](https://aismy.github.io/2021/08/17/MYSQL/)
- [https://www.yuque.com/heychu/akbndd/zhuxqd](https://www.yuque.com/heychu/akbndd/zhuxqd)
- 3. [https://www.yuque.com/heychu/akbndd/zhuxqd](https://www.yuque.com/heychu/akbndd/zhuxqd)
https://www.bilibili.com/video/BV1Kr4y1i7ru?p=75&spm_id_from=pageDriver
\ No newline at end of file
https://www.bilibili.com/video/BV1Kr4y1i7ru?p=79&spm_id_from=pageDriver
\ No newline at end of file
blog/mysq-advance/mysql-index.md
浏览文件 @ 517683aa
......@@ -355,4 +355,515 @@ mysql> show index from tb_user;
| tb_user | 1 | idx_user_email | 1 | email | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
+---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
7 rows in set (0.00 sec)
```
\ No newline at end of file
```
## 5、SQL性能分析
### 5.1、SQL执行频次
```sql
-- 查看服务器状态信息
show [session|global] status
-- 查看当前数据库的CURD（insert、update、delete、select）访问频次
-- 7个下划线
show global status like 'Com_______';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_binlog | 0 |
| Com_commit | 62 |
| Com_delete | 4 |
| Com_import | 0 |
| Com_insert | 32 |
| Com_repair | 0 |
| Com_revoke | 0 |
| Com_select | 1967 |
| Com_signal | 0 |
| Com_update | 52 |
| Com_xa_end | 0 |
+---------------+-------+
11 rows in set (0.01 sec)
```
重点关注以下4个指标：
- Com_delete
- Com_insert
- Com_select
- Com_update
### 5.2、慢查询日志
慢查询日志记录了所有执行时间超过指定参数(long_query_time，单位：秒，默认10秒)的所有SQL语句的日志
MySQL的慢查询日志默认没有开启
```sql
show variables like 'slow_query_log';
+----------------+-------+
| Variable_name | Value |
+----------------+-------+
| slow_query_log | OFF |
+----------------+-------+
1 row in set (0.01 sec)
```
查找`my.cnf`文件路径
```bash
$ mysql --help|grep 'my.cnf'
```
开启MySQL的慢查询日志，需要在MySQL的配置文件(/etc/my.cnf)中配置如下信息
```bash
# vim /etc/my.cnf
# 开启慢查询日志开关
slow_query_log=1
# 设置慢查询时间为2秒，SQL语句执行时间超过2秒，就会视为慢查询，记录慢查询日志
long_query_time=2
```
修改参数后，重启MySQL服务
```bash
systemctl restart mysqld
```
mac环境下：
配置文件路径：`/usr/local/etc/my.cnf`
重启服务
```bash
mysql.server restart
```
```sql
show variables like 'slow_query_log';
+----------------+-------+
| Variable_name | Value |
+----------------+-------+
| slow_query_log | ON |
+----------------+-------+
1 row in set (0.01 sec)
```
查看慢查询日志信息
```sql
mysql> show variables like 'slow_query_log_file';
+---------------------+-------------------------------------------------+
| Variable_name | Value |
+---------------------+-------------------------------------------------+
| slow_query_log_file | /usr/local/var/mysql/localhost-slow.log |
+---------------------+-------------------------------------------------+
1 row in set (0.00 sec)
```
查看慢日志
```bash
tail -f /usr/local/var/mysql/localhost-slow.log
# Time: 2022-05-06T14:41:31.330012Z
# User@Host: root[root] @ localhost [] Id: 8
# Query_time: 0.000408 Lock_time: 0.000184 Rows_sent: 5 Rows_examined: 5
SET timestamp=1651848091;
select * from tb_student;
```
如果看不到效果，可以设置一个较小的慢查询时间
```bash
long_query_time=0.0001
```
### 5.3、profile详情
了解时间都耗费在哪里
通过`have_profiling`参数，可以查看当前MySQL是否支持profile操作
```sql
mysql> select @@have_profiling;
+------------------+
| @@have_profiling |
+------------------+
| YES |
+------------------+
1 row in set, 1 warning (0.00 sec)
```
默认profiling是关闭的， 通过set语句在session/global级别开启profiling
```sql
select @@profiling;
+-------------+
| @@profiling |
+-------------+
| 0 |
+-------------+
1 row in set, 1 warning (0.00 sec)
-- 开启profiling
set profiling = 1;
```
查看执行耗时
```sql
-- 查看每一条SQL的耗时基本操作
show profiles;
-- 查看指定query_id的SQL语句各个阶段的耗时情况
show profile for query <query_id>;
-- 查看指定query_id 的SQL语句CPU的使用情况
show profile cpu for query <query_id>;
```
示例
```sql
mysql> show profiles;
+----------+------------+--------------------------+
| Query_ID | Duration | Query |
+----------+------------+--------------------------+
| 1 | 0.00282500 | select * from tb_student |
+----------+------------+--------------------------+
1 row in set, 1 warning (0.00 sec)
mysql> show profile for query 1;
+--------------------------------+----------+
| Status | Duration |
+--------------------------------+----------+
| starting | 0.000109 |
| Executing hook on transaction | 0.000028 |
| starting | 0.000016 |
| checking permissions | 0.000012 |
| Opening tables | 0.000069 |
| init | 0.000036 |
| System lock | 0.000027 |
| optimizing | 0.000012 |
| statistics | 0.000048 |
| preparing | 0.000021 |
| executing | 0.000006 |
| Sending data | 0.000060 |
| end | 0.000012 |
| query end | 0.000008 |
| waiting for handler commit | 0.000015 |
| closing tables | 0.000017 |
| freeing items | 0.000031 |
| logging slow query | 0.002269 |
| cleaning up | 0.000029 |
+--------------------------------+----------+
19 rows in set, 1 warning (0.01 sec)
mysql> show profile cpu for query 1;
+--------------------------------+----------+----------+------------+
| Status | Duration | CPU_user | CPU_system |
+--------------------------------+----------+----------+------------+
| starting | 0.000109 | 0.000071 | 0.000012 |
| Executing hook on transaction | 0.000028 | 0.000012 | 0.000010 |
| starting | 0.000016 | 0.000012 | 0.000004 |
| checking permissions | 0.000012 | 0.000009 | 0.000003 |
| Opening tables | 0.000069 | 0.000052 | 0.000016 |
| init | 0.000036 | 0.000019 | 0.000011 |
| System lock | 0.000027 | 0.000020 | 0.000007 |
| optimizing | 0.000012 | 0.000009 | 0.000004 |
| statistics | 0.000048 | 0.000022 | 0.000024 |
| preparing | 0.000021 | 0.000019 | 0.000003 |
| executing | 0.000006 | 0.000004 | 0.000002 |
| Sending data | 0.000060 | 0.000058 | 0.000002 |
| end | 0.000012 | 0.000007 | 0.000004 |
| query end | 0.000008 | 0.000006 | 0.000003 |
| waiting for handler commit | 0.000015 | 0.000012 | 0.000003 |
| closing tables | 0.000017 | 0.000015 | 0.000002 |
| freeing items | 0.000031 | 0.000015 | 0.000017 |
| logging slow query | 0.002269 | 0.000042 | 0.001699 |
| cleaning up | 0.000029 | 0.000014 | 0.000015 |
+--------------------------------+----------+----------+------------+
19 rows in set, 1 warning (0.00 sec)
```
### 5.4、explain 执行计划
获取MySQL如何执行select语句信息，包括在select语句执行过程中表如何连接和连接的顺序
```sql
explain/desc select 字段列表 from 表名 where 条件;
-- eg
explain select * from tb_user where id = 1;
+----+-------------+---------+------------+-------+---------------+---------+---------+-------+------+----------+-------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+---------------+---------+---------+-------+------+----------+-------+
| 1 | SIMPLE | tb_user | NULL | const | PRIMARY | PRIMARY | 4 | const | 1 | 100.00 | NULL |
+----+-------------+---------+------------+-------+---------------+---------+---------+-------+------+----------+-------+
1 row in set, 1 warning (0.00 sec)
```
字段含义
id: select 查询的序列号，表示查询中执行select子句或者是操作表的顺序
- id相同，执行顺序从上到下；
- id不同，值越大，越先执行。
select_type 表示SElect 类型，常见取值
- simple 简单表，即不使用表连接或者子查询
- primary 主查询，即外层的查询
- union union中的第二个或者后面的查询语句
- subquery select/where之后包含了子查询等
type 表示连接类型
- 性能由好到差：null, system,const(主键、唯一索引),eq_ref,ref(非唯一索引),range,index,all
possible_key 可能用到的索引，一个或多个
key 实际使用的索引，如果为null，则没有使用索引
key_len 表示索引中使用的字节数，该值为索引字段最大可能长度，并非实际使用长度，在不损失精确性的前提下，长度越短越好
rows MySQL认为必须要执行查询的行数，在innoDB引擎的表中，是一个估计值，可能并不总是准确的
filtered 表示返回结果的行数，占需读取行数的百分比，值越大越好
extra 额外信息
初始化测试数据
```sql
-- 学生表和课程表行成多对多的关系
create table tb_student(
id int primary key auto_increment,
name varchar(20)
) comment '学生表';
create table tb_course(
id int primary key auto_increment,
name varchar(20)
) comment '课程表';
create table tb_student_course(
id int primary key auto_increment,
student_id int,
course_id int
) comment '学生课程关联表';
insert into tb_student (name) values ('张飞'), ('关羽'), ('刘备'), ('曹操'), ('孙权');
insert into tb_course (name) values ('语文'), ('数学'), ('英语'), ('历史'), ('化学');
insert into tb_student_course (student_id, course_id) values (1, 1), (1, 2), (2, 1), (2, 4), (3, 4), (4, 2);
mysql> select * from tb_student;
+----+--------+
| id | name |
+----+--------+
| 1 | 张飞 |
| 2 | 关羽 |
| 3 | 刘备 |
| 4 | 曹操 |
| 5 | 孙权 |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from tb_course;
+----+--------+
| id | name |
+----+--------+
| 1 | 语文 |
| 2 | 数学 |
| 3 | 英语 |
| 4 | 历史 |
| 5 | 化学 |
+----+--------+
5 rows in set (0.00 sec)
mysql> select * from tb_student_course;
+----+------------+-----------+
| id | student_id | course_id |
+----+------------+-----------+
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 2 | 1 |
| 4 | 2 | 4 |
| 5 | 3 | 4 |
| 6 | 4 | 2 |
+----+------------+-----------+
6 rows in set (0.00 sec)
```
查看执行计划
```sql
select s.*, c.* from tb_student s, tb_course c, tb_student_course sc
where s.id = sc.student_id and c.id = sc.course_id;
+----+--------+----+--------+
| id | name | id | name |
+----+--------+----+--------+
| 1 | 张飞 | 1 | 语文 |
| 1 | 张飞 | 2 | 数学 |
| 2 | 关羽 | 1 | 语文 |
| 2 | 关羽 | 4 | 历史 |
| 3 | 刘备 | 4 | 历史 |
| 4 | 曹操 | 2 | 数学 |
+----+--------+----+--------+
6 rows in set (0.00 sec)
-- 查看执行计划
mysql> explain select s.*, c.* from tb_student s, tb_course c, tb_student_course sc
-> where s.id = sc.student_id and c.id = sc.course_id;
+----+-------------+-------+------------+--------+---------------+---------+---------+-------------------+------+----------+----------------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+--------+---------------+---------+---------+-------------------+------+----------+----------------------------------------------------+
| 1 | SIMPLE | s | NULL | ALL | PRIMARY | NULL | NULL | NULL | 5 | 100.00 | NULL |
| 1 | SIMPLE | sc | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 16.67 | Using where; Using join buffer (Block Nested Loop) |
| 1 | SIMPLE | c | NULL | eq_ref | PRIMARY | PRIMARY | 4 | data.sc.course_id | 1 | 100.00 | NULL |
+----+-------------+-------+------------+--------+---------------+---------+---------+-------------------+------+----------+----------------------------------------------------+
3 rows in set, 1 warning (0.00 sec)
```
查询选修了`语文`课程的学生，通过子查询实现
```sql
select id from tb_course where name = '语文';
+----+
| id |
+----+
| 1 |
+----+
1 row in set (0.00 sec)
select student_id from tb_student_course where course_id = 1;
+------------+
| student_id |
+------------+
| 1 |
| 2 |
+------------+
2 rows in set (0.00 sec)
select * from tb_student where id in (1, 2);
+----+--------+
| id | name |
+----+--------+
| 1 | 张飞 |
| 2 | 关羽 |
+----+--------+
2 rows in set (0.00 sec)
-- 组合成子查询语句
select * from tb_student where id in (
select student_id from tb_student_course where course_id = (
select id from tb_course where name = '语文'
)
);
+----+--------+
| id | name |
+----+--------+
| 1 | 张飞 |
| 2 | 关羽 |
+----+--------+
2 rows in set (0.00 sec)
-- 查看执行计划
explain select * from tb_student where id in (
select student_id from tb_student_course where course_id = (
select id from tb_course where name = '语文'
)
);
+----+-------------+-------------------+------------+------+---------------+------+---------+------+------+----------+----------------------------------------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------------------+------------+------+---------------+------+---------+------+------+----------+----------------------------------------------------------------------------+
| 1 | PRIMARY | tb_student | NULL | ALL | PRIMARY | NULL | NULL | NULL | 5 | 100.00 | NULL |
| 1 | PRIMARY | tb_student_course | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 16.67 | Using where; FirstMatch(tb_student); Using join buffer (Block Nested Loop) |
| 3 | SUBQUERY | tb_course | NULL | ALL | NULL | NULL | NULL | NULL | 5 | 20.00 | Using where |
+----+-------------+-------------------+------------+------+---------------+------+---------+------+------+----------+----------------------------------------------------------------------------+
3 rows in set, 1 warning (0.00 sec)
```
更多示例
```sql
mysql> select 'A';
+---+
| A |
+---+
| A |
+---+
1 row in set (0.00 sec)
mysql> explain select 'A';
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+----------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+----------------+
| 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+----------------+
1 row in set, 1 warning (0.01 sec)
```
```sql
mysql> select * from tb_user;
+----+--------+-------------+------------+------+--------+-------------+
| id | name | phone | profession | age | status | email |
+----+--------+-------------+------------+------+--------+-------------+
| 1 | 张飞 | 15210231227 | 美术 | 23 | 1 | 123@qq.com |
| 2 | 关羽 | 15210231297 | 物理 | 24 | 1 | 3339@qq.com |
| 3 | 刘备 | 15214231297 | 数学 | 25 | 0 | 666@qq.com |
| 4 | 孙权 | 15215231297 | 语文 | 20 | 1 | 111@qq.com |
+----+--------+-------------+------------+------+--------+-------------+
4 rows in set (0.00 sec)
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 | 4 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 0 | idx_user_phone | 1 | phone | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_name | 1 | name | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_profession_age_status | 1 | profession | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_profession_age_status | 2 | age | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_profession_age_status | 3 | status | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_email | 1 | email | A | 4 | NULL | NULL | YES | BTREE | | | YES | NULL |
+---------+------------+--------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
7 rows in set (0.05 sec)
mysql> explain select * from tb_user where phone = '15210231227';
+----+-------------+---------+------------+-------+----------------+----------------+---------+-------+------+----------+-------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+----------------+----------------+---------+-------+------+----------+-------+
| 1 | SIMPLE | tb_user | NULL | const | idx_user_phone | idx_user_phone | 47 | const | 1 | 100.00 | NULL |
+----+-------------+---------+------------+-------+----------------+----------------+---------+-------+------+----------+-------+
1 row in set, 1 warning (0.01 sec)
mysql> explain select * from tb_user where name = '张飞';
+----+-------------+---------+------------+------+---------------+---------------+---------+-------+------+----------+-------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+---------------+---------------+---------+-------+------+----------+-------+
| 1 | SIMPLE | tb_user | NULL | ref | idx_user_name | idx_user_name | 83 | const | 1 | 100.00 | NULL |
+----+-------------+---------+------------+------+---------------+---------------+---------+-------+------+----------+-------+
1 row in set, 1 warning (0.01 sec)
mysql> explain select count(*) from tb_user;
+----+-------------+---------+------------+-------+---------------+----------------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+---------------+----------------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | index | NULL | idx_user_phone | 47 | NULL | 4 | 100.00 | Using index |
+----+-------------+---------+------------+-------+---------------+----------------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
```
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