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HomeDatabaseMysql TutorialMYSQL5.7.9开启慢查询日志的技巧_MySQL

用MYSQL 5.7.9 作为ZABBIX 2.4.7 的监控数据库. 前段时间开启了慢查询日志, 后来发现慢查询日志膨胀到了700M

查看最后100条 大部分都是 0.1 秒的 后来想改, 以前是动态设置的 set global slow_query_log=1; 方式的 .

然后想直接用配置文件/etc/my.cnf 配慢查询

# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at % of total RAM for dedicated server, else %.
innodb_buffer_pool_size = M
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
# These are commonly set, remove the # and set as required.
basedir = /LANMP/mysql
datadir = /MYSQLDATA/data
port = 
# server_id = .....
socket = /tmp/mysql.sock
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
join_buffer_size = M
sort_buffer_size = M
read_rnd_buffer_size = M
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
character_set_server=utf
init_connect='SET NAMES utf'
slow_query_log = 
slow_query_log_file = /MYSQLDATA/mysql_slow_query.log
long_query_time = 
log_queries_not_using_indexes = ON

反复启动了好多次 service mysqld restart

mysql> show variables like '%query%';
+------------------------------+---------------------------------+
| Variable_name | Value |
+------------------------------+---------------------------------+
| binlog_rows_query_log_events | OFF |
| ft_query_expansion_limit | 20 |
| have_query_cache | YES |
| long_query_time | 5.000000 |
| query_alloc_block_size | 8192 |
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 1048576 |
| query_cache_type | OFF |
| query_cache_wlock_invalidate | OFF |
| query_prealloc_size | 8192 |
| slow_query_log | ON |
| slow_query_log_file | /MYSQLDATA/mysql_slow_query.log |
+------------------------------+---------------------------------+
13 rows in set (0.00 sec)

老是OFF 状态 而其他的 LONG_QUERY_TIME 得到了改变 5秒

用动态方式设置 报错

mysql> set global slow_query_log=1;
ERROR 29 (HY000): File '/MYSQLDATA/mysql_slow_query.log' not found (Errcode: 13 - Permission denied)

对我已经把它给删了, 为傻不自己创建个?

只好自己touch 一个

还是报错 ?

ps -ef |grep mysqld 发现 还有个mysql用户启动了mysql

看来 是用mysql用户读取慢查询日志的 用户权限问题啦

代码如下:


show variables like '%slow%';

执行结果会把是否开启慢查询、慢查询的秒数、慢查询日志等信息打印在屏幕上。

第三步:执行一次慢查询操作

其实想要执行一次有实际意义的慢查询比较困难,因为在自己测试的时候,就算查询有20万条数据的海量表,也只需要0.几秒。我们可以通过如下语句代替:

代码如下:


SELECT SLEEP(10);

第四步:查看慢查询的数量

通过如下sql语句,来查看一共执行过几次慢查询:

show global status like '%slow%';

mysql日志的配置:

注意:这些日文件在mysql重启的时候才会生成#记录所有sql语句

log=E:/mysqllog/mysql.log
#记录数据库启动关闭信息,以及运行过程中产生的错误信息
log-error=E:/mysqllog/myerror.log
# 记录除select语句之外的所有sql语句到日志中,可以用来恢复数据文件
log-bin=E:/mysqllog/bin
#记录查询慢的sql语句
log-slow-queries=E:/mysqllog/slow.log 
#慢查询时间
long_query_time=0.5

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