Mysql管理必备工具Maatkit详解之十二(mk-query-digest)

mk-query-digest 一个功能很强大的工具，能分析慢查询日志，也可以对当前的语句进行分析等。安装方法查看这里。

一、分析慢查询日志,生成报表
mysql通过log-slow-queries和long_query_time参数来记录慢查询，默认的格式如下：

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# Time: 090909 4:34:28
# User@Host: sparty[sparty] @ [localhost]
# Query_time: 18 Lock_time: 0 Rows_sent: 5 Rows_examined: 52830
select * from test;
# Time: 090909 14:04:24
# User@Host: sparty[sparty] @ [localhost]
# Query_time: 20 Lock_time: 0 Rows_sent: 10 Rows_examined: 2500284
select * from test2;

每产生一条慢查询记录一行，分析起来不直观，也无法进行统计。mk-query-digest能对slow log进行了统计和分析产生报告，可以更具自己的需要，分析出想要的结果。例如

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mk-query-digest --limit 2 --select Query_time,Lock_time,Rows_sent,Rows_examined,ts slow.log \
|grep -v '1us' |grep -v '10us'|grep -v '1ms'|grep -v '10ms'|grep -v '100ms' \
|grep -v '1s'|grep -v '10s'|grep -v 'SHOW'|grep -v '100us'|grep -v 'EXPLAIN'

# Overall: 3 total, 2 unique, 0.00 QPS, 0.00x concurrency ________________
# total min max avg 95% stddev median
# Exec time 78s 8s 44s 26s 42s 14s 25s
# Lock time 2ms 0 2ms 588us 2ms 822us 0
# Rows sent 23.87M 1 11.93M 7.96M 11.87M 5.59M 11.87M
# Rows exam 35.80M 11.93M 11.93M 11.93M 11.87M 0 11.87M
# Time range 2009-05-20 20:33:59 to 2009-05-27 14:50:13

# Query 1: 0.08 QPS, 2.68x concurrency, ID 0x67A347A2812914DF at byte 1240
# This item is included in the report because it matches --limit.
# pct total min max avg 95% stddev median
# Count 66 2
# Exec time 89 70s 26s 44s 35s 44s 13s 35s
# Lock time 0 0 0 0 0 0 0 0
# Rows sent 99 23.87M 11.93M 11.93M 11.93M 11.93M 0.71 11.93M
# Rows exam 66 23.87M 11.93M 11.93M 11.93M 11.93M 0.71 11.93M
# Time range 2009-05-27 14:49:47 to 2009-05-27 14:50:13
# Query_time distribution
# Tables
SELECT /*!40001 SQL_NO_CACHE */ * FROM `test`\G

# Query 2: 0 QPS, 0x concurrency, ID 0x92203A59492D2ECF at byte 0 ________
# This item is included in the report because it matches --limit.
# pct total min max avg 95% stddev median
# Count 33 1
# Exec time 10 8s 8s 8s 8s 8s 0 8s
# Lock time 100 2ms 2ms 2ms 2ms 2ms 0 2ms
# Rows sent 0 1 1 1 1 1 0 1
# Rows exam 33 11.93M 11.93M 11.93M 11.93M 11.93M 0 11.93M
# Time range 2009-05-20 20:33:59 to 2009-05-20 20:33:59
# Query_time distribution
# Tables
select count(*) from test where t1=20 and t2=100\G

# Rank Query ID Response time Calls R/Call Item
# ==== ================== ================ ======= ========== ====
# 1 0x67A347A2812914DF 69.7409 89.4% 2 34.870474 SELECT test
# 2 0x92203A59492D2ECF 8.2742 10.6% 1 8.274248 SELECT test

报表的输出分三部分，开头部分是整个报表的综合统计。中间部分把单独的Query进行统计，按照total Exec time从高到低排序。结尾部分是输出的每条Query的一些统计。

解释一下主要参数：
-limit 指输出耗时最多的Query的条数限制。
-select 选择需要统计的指标。

二、对当前的查询进行统计分析

mk-query-digest也能使用–processlist参数，对指定mysql的当前Query进行统计分析，例如

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mk-query-digest –processlist h=localhost -u sg -p

然后在CTRL+C结束，将对这段时间h=localhost里所进行的所有Query进行统计分析并生成报表，报表的输出和上面介绍的一样。

三、分析慢查询日志，将结果导入到指定表。

mk-query-digest也能使用–review参数，将慢查询日志的分析结果插入到指定表中。
首先需要创建表，存放分析结果：

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CREATE TABLE query_review (
checksum BIGINT UNSIGNED NOT NULL PRIMARY KEY,
fingerprint TEXT NOT NULL,
sample TEXT NOT NULL,
first_seen DATETIME,
last_seen DATETIME,
reviewed_by VARCHAR(20),
reviewed_on DATETIME,
comments TEXT
)
COLUMN MEANING
=========== ===============
checksum A 64-bit checksum of the query fingerprint
fingerprint The abstracted version of the query; its primary key
sample The query text of a sample of the class of queries
first_seen The smallest timestamp of this class of queries
last_seen The largest timestamp of this class of queries
reviewed_by Initially NULL; if set, query is skipped thereafter
reviewed_on Initially NULL; not assigned any special meaning
comments Initially NULL; not assigned any special meaning例如：

mk-query-digest --review h=host1,D=test,t=query_review /path/to/slow.log

mysql> use test;
Database changed
mysql> select * from query_review\G;
*************************** 1. row ***************************
checksum: 7467891370387641567
fingerprint: mysqldump
sample: SELECT /*!40001 SQL_NO_CACHE */ * FROM `test`
first_seen: 2009-05-27 14:49:47
last_seen: 2009-05-27 14:50:13
reviewed_by: NULL
reviewed_on: NULL
comments: NULL
*************************** 2. row ***************************
checksum: 10529480083946417871
fingerprint: select count(*) from test where test1=? and test2=?
sample: select count(*) from test where test1=20 and test2=100
first_seen: 2009-05-20 20:33:59
last_seen: 2009-05-20 20:33:59
reviewed_by: NULL
reviewed_on: NULL
comments: NULL
2 rows in set (0.00 sec)

四、查找未走索引的语句

mk-query-digest还可以用来找出当前数据库未走索引的语句，例如我使用下面命令：

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tcpdump -i bond0 port 3306 -s 65535 -x -n -q -tttt | mk-query-digest –type tcpdump –filter '($event->{No_index_used} || $event->{No_good_index_used})'

然后在CTRL+C结束，将生成下面的报告。

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tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on bond0, link-type EN10MB (Ethernet), capture size 65535 bytes
3 packets captured
3 packets received by filter
0 packets dropped by kernel
# Caught SIGINT.
# 170ms user time, 20ms system time, 12.00M rss, 73.26M vsz
# Overall: 1 total, 1 unique, 0 QPS, 0x concurrency ______________________
# total min max avg 95% stddev median
# Exec time 223us 223us 223us 223us 223us 0 223us
# Time range 2009-09-16 09:22:50.637146 to 2009-09-16 09:22:50.637146
# bytes 26 26 26 26 26 0 26
# Rows affe 0 0 0 0 0 0 0
# Warning c 0 0 0 0 0 0 0
# 100% (1) No_index_used

# Query 1: 0 QPS, 0x concurrency, ID 0x3D8C074C26D05CD7 at byte 0 ________
# This item is included in the report because it matches --limit.
# pct total min max avg 95% stddev median
# Count 100 1
# Exec time 100 223us 223us 223us 223us 223us 0 223us
# Hosts 1 10.0.0.203
# Time range 2009-09-16 09:22:50.637146 to 2009-09-16 09:22:50.637146
# bytes 100 26 26 26 26 26 0 26
# Errors 1 none
# Rows affe 0 0 0 0 0 0 0 0
# Warning c 0 0 0 0 0 0 0 0
# 100% (1) No_index_used

select * from test\G

# Rank Query ID Response time Calls R/Call Item
# ==== ================== ================ ======= ========== ====
# 1 0x3D8C074C26D05CD7 0.0002 100.0% 1 0.000223 SELECT test

很明显，使用tcpdump只能对本地的mysql进行监听，一目了然的找到了哪条sql是没走索引的。

最后，我们在看下这个工具的帮助选项：

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