背景
从MySQL.slow_log 获取慢查询日志很慢,该表是csv表,没有索引。 想添加索引来加速访问,而csv引擎不能添加索引(csv引擎存储是以逗号分割的文本来存储的),只能改存储引擎来添加索引了
mysql.slow_log表能改成myisam,不能改成innodb
mysql> set global slow_query_log=off;
Query OK, 0 rows affected (0.00 sec)
mysql> alter table mysql.slow_log engine=innodb;
ERROR 1579 (HY000): This storage engine cannot be used for log tables"
mysql> alter table mysql.slow_log engine=myisam;
Query OK, 33760 rows affected (0.37 sec)
Records: 33760 Duplicates: 0 Warnings: 0
mysql.general_log也不能改成innodb
mysql> alter table mysql.general_log engine=myisam;
Query OK, 242956 rows affected (2.41 sec)
Records: 242956 Duplicates: 0 Warnings: 0
mysql> alter table mysql.general_log engine=innodb;
ERROR 1579 (HY000): This storage engine cannot be used for log tables"
官方文档
官方文档说明,日志表只支持csv引擎和myisam引擎。 为什么不支持innodb引擎并未说明
基于什么来考虑不支持innodb表的了? 像朋友请教了下
估计是日志表 这种引擎会耗费大量的redo, undo 资源吧 这是没有必要的。。。这些数据不重要。。
更改日志表存储引擎并添加索引
mysql.general_log表
set sql_log_bin=0;
SET @old_log_state = @@global.general_log;
SET GLOBAL general_log = 'OFF';
ALTER TABLE mysql.general_log ENGINE = MyISAM;
SET GLOBAL general_log = @old_log_state;
mysql.slow_log表
set sql_log_bin=0;
set @old_slow_log_state=@@global.slow_query_log;
set global slow_query_log='OFF';
ALTER TABLE mysql.slow_log ENGINE = MyISAM;
alter table mysql.slow_log add index idx_query_time(query_time);
set global slow_query_log=@old_slow_log_state;
注意问题
更改日志表的存储引擎需要先关闭日志表,还需要不记录会话的binlog日志 不然,主从复制中,从库会出现sql线程错误
LAST_ERROR_MESSAGE: Worker 1 failed executing transaction '5a459629-1e13-11e9-a99d-74eacb7427c5:377210591' at master log mysql-bin.001278, end_log_pos 40623782; Error 'You cannot 'ALTER' a log table if logging is enabled' on query. Default database: ''. Query: 'ALTER TABLE mysql.slow_log ENGINE = MyISAM'
归档日志表 归档mysql.general_log表
USE mysql;
DROP TABLE IF EXISTS general_log2;
CREATE TABLE general_log2 LIKE general_log;
RENAME TABLE general_log TO general_log_backup, general_log2 TO general_log;
归档mysql.slow_log表
USE mysql;
DROP TABLE IF EXISTS slow_log2;
CREATE TABLE slow_log2 LIKE slow_log;
RENAME TABLE slow_log TO slow_log_backup, slow_log2 TO slow_log;
参考
Selecting General Query Log and Slow Query Log Output Destinations