MySQL 中的服务器配置和状态详解(MySQL Server Configuration and Status)

[root@localhost ~]# mysqld --verbose --help

[root@localhost ~]# ps aux | grep mysqld
mysql 2423 0.6 23.7 1836108 433416 ? Ssl 13:01 3:27 /usr/libexec/mysqld --basedir=/usr

#这个选项是配置在服务脚本中的
[root@localhost ~]# systemctl cat mysqld.service | grep basedir
# Note: we set --basedir to prevent probes that might trigger SELinux alarms,
ExecStart=/usr/libexec/mysqld --basedir=/usr

[root@localhost ~]# mysqld --print-defaults
/usr/libexec/mysqld would have been started with the following arguments:
--default_authentication_plugin=mysql_native_password --datadir=/var/lib/mysql 
--socket=/var/lib/mysql/mysql.sock --log-error=/var/log/mysql/mysqld.log --pid-file=/run/mysqld/mysqld.pid
#这些选项都是写在配置文件中的
[root@localhost ~]# cat /etc/my.cnf.d/mysql-server.cnf
......
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysql/mysqld.log
pid-file=/run/mysqld/mysqld.pid
[root@localhost ~]# cat /etc/my.cnf.d/mysql-default-authentication-plugin.cnf
......
[mysqld]
default_authentication_plugin=mysql_native_password

[root@localhost ~]# /usr/libexec/mysqld --basedir=/usr --max_connections=202 --user=mysql &
[1] 9358
#查看
mysql> show variables like 'max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 202   |
+-----------------+-------+
1 row in set (0.01 sec)

[root@localhost ~]# vim /etc/my.cnf
[mysqld]
max_connections=200
#查看，此时配置在在配置文件中可见，但并没有生效，需要重启
[root@localhost ~]# mysqld --print-defaults
/usr/libexec/mysqld would have been started with the following arguments:
--default_authentication_plugin=mysql_native_password --datadir=/var/lib/mysql 
--socket=/var/lib/mysql/mysql.sock --log-error=/var/log/mysql/mysqld.log --pid-file=/run/mysqld/mysqld.pid --max_connections=200
#查看选项，因为此项与变量同名
mysql> show variables like 'max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 151   |
+-----------------+-------+
1 row in set (0.00 sec)
#重启服务
[root@localhost ~]# systemctl restart mysqld.service
#再次查看
mysql> show variables like 'max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 200   |
+-----------------+-------+
1 row in set (0.00 sec)​​​​​​​​​​​​​
#配置文件中的服务器选项，可以写下划线，也可以写中划线
[root@localhost ~]# vim /etc/my.cnf
[mysqld]
#max_connections=200
max-connections=201
#重启服务
[root@localhost ~]# systemctl restart mysqld.service
#查看
mysql> show variables like 'max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 201   |
+-----------------+-------+
1 row in set (0.00 sec)

[root@localhost ~]# vim /etc/my.cnf
[mysqld]
#max_connections=200
max-connections=201
character_set_database=utf8
#无法启动服务，因为 character_set_database 不是服务器选项
[root@localhost ~]# systemctl restart mysqld.service
Job for mysqld.service failed because the control process exited with error code.
See "systemctl status mysqld.service" and "journalctl -xe" for details.
#查看具体错误信息
[root@localhost ~]# tail /var/log/mysql/mysqld.log

#查看所有全局变量
mysql> show global variables 630
#查看所有变量，包括session和global
mysql> show session variables
mysql> show variables
#查看指定变量 SHOW VARIABLES LIKE 'VAR_NAME';
mysql> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | ON    |
+---------------+-------+
1 row in set (0.00 sec)
mysql> show variables like 'sql_log_%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | ON    |
| sql_log_off   | OFF   |
+---------------+-------+
2 rows in set (0.00 sec)
#查看指定变量 SELECT @@VAR_NAME;
mysql> select @@sql_log_bin;
+---------------+
| @@sql_log_bin |
+---------------+
| 1             |
+---------------+
1 row in set (0.00 sec)

mysql> help set

SET GLOBAL system_var_name=value;
SET @@global.system_var_name=value;

#终端
mysql> show variables like 'sql_warnings';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_warnings  | OFF   |
+---------------+-------+
1 row in set (0.00 sec)
#终端B
mysql> select @@sql_warnings;
+----------------+
| @@sql_warnings |
+----------------+
| 0              |
+----------------+
1 row in set (0.00 sec)
#终端A中修改
mysql> set global sql_warnings=1;
Query OK, 0 rows affected (0.00 sec)
#终端A中查看
mysql> show variables like 'sql_warnings';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_warnings  | OFF   |
+---------------+-------+
1 row in set (0.01 sec)
#终端B中查看
mysql> select @@sql_warnings;
+----------------+
| @@sql_warnings |
+----------------+
| 0              |
+----------------+
1 row in set (0.00 sec)
#重新建立连接再查看
mysql> select @@sql_warnings;
+----------------+
| @@sql_warnings |
+----------------+
| 1              |
+----------------+
1 row in set (0.00 sec)

#终端A
mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 100   |
+------------------------+-------+
1 row in set (0.01 sec)
#终端B
mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 100   |
+------------------------+-------+
1 row in set (0.01 sec)
#在终端A中修改
mysql> set mysqlx_max_connections=108;
ERROR 1229 (HY000): Variable 'mysqlx_max_connections' is a GLOBAL variable and should be set with SET GLOBAL
mysql> set global mysqlx_max_connections=108;
Query OK, 0 rows affected (0.00 sec)
#终端A再次查看
mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 108   |
+------------------------+-------+
1 row in set (0.00 sec)
#终端B再次查看
mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 108   |
+------------------------+-------+
1 row in set (0.00 sec)

SET [SESSION] system_var_name=value;
SET @@[session.]system_var_name=value;
​​​​​​
#终端A
mysql> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | ON    |
+---------------+-------+
1 row in set (0.00 sec)
#终端B
mysql> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | ON    |
+---------------+-------+
1 row in set (0.00 sec)
#在终端A中修改
mysql> set sql_log_bin=0;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | OFF   |
+---------------+-------+
1 row in set (0.01 sec)
#再次在终端B中查看，并不受影响
mysql> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin   | ON    |
+---------------+-------+
1 row in set (0.00 sec)
#重新连接，也不受影响

#该项的 Dynamic 列值为 No，不能动态修改
mysql> show variables like 'admin_port';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| admin_port    | 33062 |
+---------------+-------+
1 row in set (0.00 sec)
mysql> set global admin_port=33063;
ERROR 1238 (HY000): Variable 'admin_port' is a read only variable

mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 108   |
+------------------------+-------+
1 row in set (0.00 sec)
#重启服务
[root@localhost ~]# systemctl restart mysqld.service
#再次查看
mysql> show variables like 'mysqlx_max_connections';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| mysqlx_max_connections | 100   |
+------------------------+-------+
1 row in set (0.00 sec)

#查看所有全局状态变量
mysql> show global status;
#查看所有状态变量，包括global和session
mysql> show status;
mysql> show session status;

mysql> show status like 'Com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select    | 2     |
+---------------+-------+
1 row in set (0.00 sec)
mysql> select * from testdb.t1;
Empty set (0.00 sec)
#查询次数增加
mysql> show status like 'Com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select    | 3     |
+---------------+-------+
1 row in set (0.00 sec)
#查看全局
mysql> show global status like 'Com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select    | 8     |
+---------------+-------+
1 row in set (0.00 sec)
#查看服务运行时长
mysql> show status like 'Uptime';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Uptime        | 2503  |
+---------------+-------+
1 row in set (0.00 sec)
mysql> show global status like 'Uptime';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Uptime        | 2507  |
+---------------+-------+
1 row in set (0.00 sec)

[root@localhost ~]# systemctl restart mysqld.service
mysql> show status like 'Com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select    | 1     |
+---------------+-------+
1 row in set (0.00 sec)
mysql> show global status like 'Uptime';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Uptime        | 4     |
+---------------+-------+
1 row in set (0.00 sec)

#查看
mysql> select @@sql_mode\G
*************************** 1. row ***************************
@@sql_mode:
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
1 row in set (0.00 sec)
#修改，此处修改重启服务后会还原，如果需要永久生效，则可以写配置文件
mysql> set @@sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> select @@sql_mode\G
*************************** 1. row ***************************
@@sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES
1 row in set (0.00 sec)