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修改my.cnf的mysqld部分:
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怎么记录mysql慢查询sql日志

Jun 07, 2016 pm 04:15 PM
mysql sql how how log Inquire Record

如何记录mysql慢查询sql日志 修改my.cnf的mysqld部分: long_query_time = 1????????????? //定义慢查询的时间1表示1秒 --log-slow-queries[=file_name]?? //记录慢查询到日志文件 --log-queries-not-using-indexes //将没使用索引的sql记录到日志文件 实例:

如何记录mysql慢查询sql日志

修改my.cnf的mysqld部分:

long_query_time = 1????????????? //定义慢查询的时间1表示1秒
--log-slow-queries[=file_name]?? //记录慢查询到日志文件
--log-queries-not-using-indexes //将没使用索引的sql记录到日志文件
实例:
[mysqld]
long_query_time = 1
log-slow-queries = /usr/local/mysql5.0.40/var/slow_query.log
log-queries-not-using-indexes = true

"too many connections"找不到问题所在,后来发现打开mysql的慢查询会有很大的帮助就搞了一个.

打开MySQL慢查询
MySQL慢查询记录日志对于跟踪PHP+MySQL体系下的MySQL负载调优问题很有用处,比如安装了很多Discuz!插件的用户,这样可以大概排查出那些插件有代码问题。其实启用MySQL的慢查询日志很简单,只需要在MySQL的配置文件里添加log-slow-queries和long_query_time两个参数即可。

今天有个朋友问我,就顺带记录上来。更多的MySQL优化信息可以查看这里:http://www.ccvita.com/category/mysql

Windows下开启MySQL慢查询
MySQL在Windows系统中的配置文件一般是是my.ini找到[mysqld]下面加上
log-slow-queries = F:\MySQL\log\mysqlslowquery.log
long_query_time = 2

Linux下启用MySQL慢查询
MySQL在Windows系统中的配置文件一般是是my.cnf找到[mysqld]下面加上
log-slow-queries=/data/mysqldata/slowquery.log
long_query_time=2

注意
log-slow-queries = F:\MySQL\log\mysqlslowquery.log为查询日志存放的位置,一般这个目录要有MySQL的运行帐号的可写权限,一般都将这个目录设置为MySQL的数据存放目录;
long_query_time=2中的2表示查询超过两秒才记录;

启用 slow log
?

有两种启用方式: 1, 在my.cnf 里 通过 log-slow-queries[=file_name] 2, 在mysqld进程启动时,指定--log-slow-queries[=file_name]选项

比较的五款常用工具
?

mysqldumpslow, mysqlsla, myprofi, mysql-explain-slow-log, mysqllogfilter

mysqldumpslow, mysql官方提供的慢查询日志分析工具. 输出图表如下

主要功能是,?统计不同慢sql的 出现次数(Count),? 执行最长时间(Time),? 累计总耗费时间(Time),? 等待锁的时间(Lock),? 发送给客户端的行总数(Rows),? 扫描的行总数(Rows),? 用户以及sql语句本身(抽象了一下格式, 比如 limit 1, 20 用 limit N,N 表示).

讲一下有用的参数:?
-s 排序选项:c 查询次数 r 返回记录行数 t 查询时间?
-t 只显示top n条查询?
mysqldumpslow -s r -t 10 slow.log?

?

mysqlsla, hackmysql.com推出的一款日志分析工具(该网站还维护了 mysqlreport, mysqlidxchk 等比较实用的mysql工具)

整体来说, 功能非常强大. 数据报表,非常有利于分析慢查询的原因, 包括执行频率, 数据量, 查询消耗等.
?
? 格式说明如下: 总查询次数 (queries total), 去重后的sql数量 (unique) 输出报表的内容排序(sorted by) 最重大的慢sql统计信息, 包括 平均执行时间, 等待锁时间, 结果行的总数, 扫描的行总数.
? Count, sql的执行次数及占总的slow log数量的百分比. Time, 执行时间, 包括总时间, 平均时间, 最小, 最大时间, 时间占到总慢sql时间的百分比. 95% of Time, 去除最快和最慢的sql, 覆盖率占95%的sql的执行时间. Lock Time, 等待锁的时间. 95% of Lock , 95%的慢sql等待锁时间. Rows sent, 结果行统计数量, 包括平均, 最小, 最大数量.
Rows examined, 扫描的行数量. Database, 属于哪个数据库 Users, 哪个用户,IP, 占到所有用户执行的sql百分比
? Query abstract, 抽象后的sql语句 Query sample, sql语句
? 除了以上的输出, 官方还提供了很多定制化参数, 是一款不可多得的好工具.
? mysql-explain-slow-log, 德国人写的一个perl脚本.
http://www.willamowius.de/mysql-tools.html

?

功能上有点瑕疵, 不仅把所有的 slow log 打印到屏幕上, 而且统计也只有数量而已. 不推荐使用. mysql-log-filter, google code上找到的一个分析工具.提供了 python 和 php 两种可执行的脚本.
http://code.google.com/p/mysql-log-filter/

?

?功能上比官方的mysqldumpslow, 多了查询时间的统计信息(平均,最大, 累计), 其他功能都与 mysqldumpslow类似.
特色功能除了统计信息外, 还针对输出内容做了排版和格式化, 保证整体输出的简洁. 喜欢简洁报表的朋友, 推荐使用一下.

myprofi, 纯php写的一个开源分析工具.项目在 sourceforge 上.
http://myprofi.sourceforge.net/

?

?

功能上, 列出了总的慢查询次数和类型, 去重后的sql语句, 执行次数及其占总的slow log数量的百分比.
从整体输出样式来看, 比mysql-log-filter还要简洁. 省去了很多不必要的内容. 对于只想看sql语句及执行次数的用户来说, 比较推荐.

总结
?

工具/功能 一般统计信息 高级统计信息 脚本 优势
mysqldumpslow 支持 不支持 perl mysql官方自带
mysqlsla 支持 支持 perl 功能强大,数据报表齐全,定制化能力强.
mysql-explain-slow-log 支持 不支持 perl
mysql-log-filter 支持 部分支持 python or php 不失功能的前提下,保持输出简洁
myprofi 支持 不支持 php 非常精
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