mysql> show variables like '%max_connections%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| max_connections | 8000 |
| mysqlx_max_connections | 100 |
+------------------------+-------+
2 rows in set (0.06 sec)
mysql> set persist max_connections=500;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like '%max_connections%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| max_connections | 500 |
| mysqlx_max_connections | 100 |
+------------------------+-------+
2 rows in set (0.00 sec)
[root@anedbtest01 ~]# cat /u01/data/ane20000/mysqld-auto.cnf|/tmp/jq
{
"Version": 1,
"mysql_server": {
"max_connections": {
"Value": "500",
"Metadata": {
"Timestamp": 1558056501802792,
"User": "root",
"Host": "localhost"
}
}
}
}
[root@anedbtest01 mysql]# cat /u01/mysql8015/etc/my_20000.cnf |grep max_connections
max_connections = 8000
查看配置文件，仍然是之前的配置max_connections = 8000
mysql> restart
mysql> show variables like '%max_connections%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| max_connections | 500 |
| mysqlx_max_connections | 100 |
+------------------------+-------+
2 rows in set (0.01 sec)
set persist更改運行時變量值，將變量設置寫入mysqld-auto.cnf數據目錄中指定的選項文件 。數據庫啓動時，會首先讀取其它配置文件my.cnf，最後纔讀取mysqld-auto.cnf文件。
不建議手動修改該文件，其有可能導致數據庫在啓動過程中因解析錯誤而失敗。如果出現這種情況，可手動刪除mysqld-auto.cnf文件或將persisted_globals_load變量設置爲off來避免該文件的加載
對於已經持久化了變量，可通過reset persist命令取消持久
注意，其只是清空mysqld-auto.cnf和performance_schema.persisted_variables中的內容，對於已經修改了的變量的值，不會產生任何影響。
mysql> RESET PERSIST max_connections;
Query OK, 0 rows affected (0.00 sec)
[root@anedbtest01 mysql]# cat /u01/data/ane20000/mysqld-auto.cnf|/tmp/jq
{
"Version": 1,
"mysql_server": {}
}
mysql> show variables like '%max_connections%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| max_connections | 500 |
| mysqlx_max_connections | 100 |
+------------------------+-------+
2 rows in set (0.00 sec)
mysql> restart;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like '%max_connections%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| max_connections | 8000 |
| mysqlx_max_connections | 100 |
+------------------------+-------+
2 rows in set (0.01 sec)
如果要改read_only 變量
mysql> show variables like 'innodb_log_file_size';
+----------------------+------------+
| Variable_name | Value |
+----------------------+------------+
| innodb_log_file_size | 1073741824 |
+----------------------+------------+
1 row in set (0.01 sec)
mysql> set persist innodb_log_file_size=2073741824;
ERROR 1238 (HY000): Variable 'innodb_log_file_size' is a read only variable
mysql> set persist_only innodb_log_file_size=2073741824;
Query OK, 0 rows affected (0.00 sec)
[root@anedbtest01 mysql]# cat /u01/data/ane20000/mysqld-auto.cnf|/tmp/jq
{
"Version": 1,
"mysql_server": {
"mysql_server_static_options": {
"innodb_log_file_size": {
"Value": "2073741824",
"Metadata": {
"Timestamp": 1558061748935792,
"User": "root",
"Host": "localhost"
}
}
}
}
}
mysql> show variables like 'innodb_log_file_size';
+----------------------+------------+
| Variable_name | Value |
+----------------------+------------+
| innodb_log_file_size | 1073741824 |
+----------------------+------------+
1 row in set (0.01 sec)
但是對於read only 的參數，修改參數後需要重啓才能生效
修改read only的變量需要額外的特權:
SYSTEM_VARIABLES_ADMIN
PERSIST_RO_VARIABLES_ADMIN
mysql> restart;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like 'innodb_log_file_size';
+----------------------+------------+
| Variable_name | Value |
+----------------------+------------+
| innodb_log_file_size | 2073034752 |
+----------------------+------------+
mysql> select * from performance_schema.variables_info where variable_source like 'PERSISTED'\G
*************************** 1. row ***************************
VARIABLE_NAME: innodb_log_file_size
VARIABLE_SOURCE: PERSISTED
VARIABLE_PATH: /u01/data/ane20000/mysqld-auto.cnf
MIN_VALUE: 4194304
MAX_VALUE: 18446744073709551615
SET_TIME: 2019-05-17 11:02:34.412763
SET_USER: root
SET_HOST: localhost
1 row in set (0.01 sec)
1 row in set (0.01 sec)