对MySQL慢查询日志进行分析的基本教程

0、首先查看当前是否开启慢查询：

（1）快速办法，运行sql语句

show variables like "%slow%" 

（2）直接去my.conf中查看。

my.conf中的配置(放在[mysqld]下的下方加入)

[mysqld]

log-slow-queries = /usr/local/mysql/var/slowquery.log
long_query_time = 1 #单位是秒
log-queries-not-using-indexes

使用sql语句来修改：不能按照my.conf中的项来修改的。修改通过"show variables like "%slow%" "
语句列出来的变量，运行如下sql：

set global log_slow_queries = on;
set global slow_query_log = on;
set global long_query_time=0.1; #设置大于0.1s的sql语句记录下来

慢查询日志文件的信息格式：

# time: 130905 14:15:59   时间是2013年9月5日 14:15:59(前面部分容易看错哦,乍看以为是时间戳)
# user@host: root[root] @ [183.239.28.174] 请求mysql服务器的客户端ip
# query_time: 0.735883 lock_time: 0.000078 rows_sent: 262 rows_examined: 262 这里表示执行用时多少秒，0.735883秒，1秒等于1000毫秒

set timestamp=1378361759;  这目前我还不知道干嘛用的
show tables from `test_db`; 这个就是关键信息，指明了当时执行的是这条语句

1、mysql 慢查询日志分析
pt-query-digest分析慢查询日志

pt-query-digest –report slow.log

报告最近半个小时的慢查询：

pt-query-digest –report –since 1800s slow.log

报告一个时间段的慢查询：

pt-query-digest –report –since ‘2013-02-10 21:48:59′ –until ‘2013-02-16 02:33:50′ slow.log

报告只含select语句的慢查询:

pt-query-digest –filter ‘$event->{fingerprint} =~ m/^select/i' slow.log

报告针对某个用户的慢查询:

pt-query-digest –filter ‘($event->{user} || “”) =~ m/^root/i' slow.log

报告所有的全表扫描或full join的慢查询:

pt-query-digest –filter ‘(($event->{full_scan} || “”) eq “yes”) || (($event->{full_join} || “”) eq “yes”)' slow.log

2、将慢查询日志的分析结果可视化
query-digest-ui
其实，这是一个非常简单和直接的工具，浏览和统计mysql慢查询，基于ajax的web界面。
配置query-digest-ui：

下载：

wget https://nodeload.github.com/kormoc/query-digest-ui/zip/master
 unzip query-digest-ui-master.zip

查询分析结果可视化步骤如下:

（1）创建相关数据库表

-- install.sql
-- create the database needed for the query-digest-ui
drop database if exists slow_query_log;
create database slow_query_log;
use slow_query_log;
 
-- create the global query review table
create table `global_query_review` (
 `checksum` bigint(20) unsigned not null,
 `fingerprint` text not null,
 `sample` longtext not null,
 `first_seen` datetime default null,
 `last_seen` datetime default null,
 `reviewed_by` varchar(20) default null,
 `reviewed_on` datetime default null,
 `comments` text,
 `reviewed_status` varchar(24) default null,
 primary key (`checksum`)
) engine=innodb default charset=utf8;
 
-- create the historical query review table
create table `global_query_review_history` (
 `hostname_max` varchar(64) not null,
 `db_max` varchar(64) default null,
 `checksum` bigint(20) unsigned not null,
 `sample` longtext not null,
 `ts_min` datetime not null default '0000-00-00 00:00:00',
 `ts_max` datetime not null default '0000-00-00 00:00:00',
 `ts_cnt` float default null,
 `query_time_sum` float default null,
 `query_time_min` float default null,
 `query_time_max` float default null,
 `query_time_pct_95` float default null,
 `query_time_stddev` float default null,
 `query_time_median` float default null,
 `lock_time_sum` float default null,
 `lock_time_min` float default null,
 `lock_time_max` float default null,
 `lock_time_pct_95` float default null,
 `lock_time_stddev` float default null,
 `lock_time_median` float default null,
 `rows_sent_sum` float default null,
 `rows_sent_min` float default null,
 `rows_sent_max` float default null,
 `rows_sent_pct_95` float default null,
 `rows_sent_stddev` float default null,
 `rows_sent_median` float default null,
 `rows_examined_sum` float default null,
 `rows_examined_min` float default null,
 `rows_examined_max` float default null,
 `rows_examined_pct_95` float default null,
 `rows_examined_stddev` float default null,
 `rows_examined_median` float default null,
 `rows_affected_sum` float default null,
 `rows_affected_min` float default null,
 `rows_affected_max` float default null,
 `rows_affected_pct_95` float default null,
 `rows_affected_stddev` float default null,
 `rows_affected_median` float default null,
 `rows_read_sum` float default null,
 `rows_read_min` float default null,
 `rows_read_max` float default null,
 `rows_read_pct_95` float default null,
 `rows_read_stddev` float default null,
 `rows_read_median` float default null,
 `merge_passes_sum` float default null,
 `merge_passes_min` float default null,
 `merge_passes_max` float default null,
 `merge_passes_pct_95` float default null,
 `merge_passes_stddev` float default null,
 `merge_passes_median` float default null,
 `innodb_io_r_ops_min` float default null,
 `innodb_io_r_ops_max` float default null,
 `innodb_io_r_ops_pct_95` float default null,
 `innodb_io_r_bytes_pct_95` float default null,
 `innodb_io_r_bytes_stddev` float default null,
 `innodb_io_r_bytes_median` float default null,
 `innodb_io_r_wait_min` float default null,
 `innodb_io_r_wait_max` float default null,
 `innodb_io_r_wait_pct_95` float default null,
 `innodb_io_r_ops_stddev` float default null,
 `innodb_io_r_ops_median` float default null,
 `innodb_io_r_bytes_min` float default null,
 `innodb_io_r_bytes_max` float default null,
 `innodb_io_r_wait_stddev` float default null,
 `innodb_io_r_wait_median` float default null,
 `innodb_rec_lock_wait_min` float default null,
 `innodb_rec_lock_wait_max` float default null,
 `innodb_rec_lock_wait_pct_95` float default null,
 `innodb_rec_lock_wait_stddev` float default null,
 `innodb_rec_lock_wait_median` float default null,
 `innodb_queue_wait_min` float default null,
 `innodb_queue_wait_max` float default null,
 `innodb_queue_wait_pct_95` float default null,
 `innodb_queue_wait_stddev` float default null,
 `innodb_queue_wait_median` float default null,
 `innodb_pages_distinct_min` float default null,
 `innodb_pages_distinct_max` float default null,
 `innodb_pages_distinct_pct_95` float default null,
 `innodb_pages_distinct_stddev` float default null,
 `innodb_pages_distinct_median` float default null,
 `qc_hit_cnt` float default null,
 `qc_hit_sum` float default null,
 `full_scan_cnt` float default null,
 `full_scan_sum` float default null,
 `full_join_cnt` float default null,
 `full_join_sum` float default null,
 `tmp_table_cnt` float default null,
 `tmp_table_sum` float default null,
 `filesort_cnt` float default null,
 `filesort_sum` float default null,
 `tmp_table_on_disk_cnt` float default null,
 `tmp_table_on_disk_sum` float default null,
 `filesort_on_disk_cnt` float default null,
 `filesort_on_disk_sum` float default null,
 `bytes_sum` float default null,
 `bytes_min` float default null,
 `bytes_max` float default null,
 `bytes_pct_95` float default null,
 `bytes_stddev` float default null,
 `bytes_median` float default null,
 unique key `hostname_max` (`hostname_max`,`checksum`,`ts_min`,`ts_max`),
 key `ts_min` (`ts_min`),
 key `checksum` (`checksum`)
) engine=innodb default charset=utf8;

（2）创建数据库账号

$ mysql -uroot -p -h 192.168.1.190 < install.sql
$ mysql -uroot -p -h 192.168.1.190 -e "grant all on slow_query_log.* to 'slowlog'@'%' identified by '123456';"

（3）配置query-digest-ui

修改数据库连接配置

cd query-digest-ui
cp config.php.example config.php
vi config.php
$reviewhost = array(
// replace hostname and database in this setting
// use host=hostname;port=portnum if not the default port
 'dsn'   => 'mysql:host=192.168.1.190;port=3306;dbname=slow_query_log',
 'user'   => 'slowlog',
 'password'  => '123456',
// see http://www.percona.com/doc/percona-toolkit/2.1/pt-query-digest.html#cmdoption-pt-query-digest--review
 'review_table' => 'global_query_review',
// this table is optional. you don't need it, but you lose detailed stats
// set to a blank string to disable
// see http://www.percona.com/doc/percona-toolkit/2.1/pt-query-digest.html#cmdoption-pt-query-digest--review-history
 'history_table' => 'global_query_review_history',
);

（4）使用pt-query-digest分析日志并将分析结果导入数据库

pt-query-digest --user=slowlog \
--password=123456 \
--review h=192.168.1.190,d=slow_query_log,t=global_query_review \
--review-history h=192.168.1.190,d=slow_query_log,t=global_query_review_history\
--no-report --limit=0% \
--filter=" \$event->{bytes} = length(\$event->{arg}) and \$event->{hostname}=\"$hostname\"" \
/usr/local/mysql/data/slow.log