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zhsgood

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发表于：

2014-12-10 10:04:48 | [全部帖] [楼主帖]

楼主

今天我们看看关于MySQL慢日志的阅读。
我们知道，如果我们的语句不够优化，那么首先MySQL的慢日志是进一步优化的离线证据，虽然里面有好多“伪慢语句”！
先不说怎么优化，如果你的日志有一条语句赌住了，那么会有不计其数的慢语句填充到MySQL的满日志里面。那么首先提炼出这些语句就非常头疼。
今天主要介绍两种工具：

1,mysqldumpslow。（咱们 MySQL自带的简单而又实用的工具）

我们先来看下mysqldumpslow的结果。

[root@localhost ~]# mysqldumpslow -r localhost-slow.log
Reading mysql slow query log from localhost-slow.log
Count: 2  Time=7.00s (14s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
select * from t_page_sample order by id desc limit N,N
Count: 1  Time=11.00s (11s)  Lock=0.00s (0s)  Rows=1.0 (1), root[root]@localhost
select count(*) from t_page_sample
Count: 1  Time=1418.00s (1418s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
insert ignore into t_page_sample select ceil(rand()*N), ceil(rand()*N), date_sub(now(),interval floor(rand()*N) day), now() from t_page_sample

比如要查找排序的慢语句：

[root@localhost ~]# mysqldumpslow -r -g "order by " localhost-slow.log
Reading mysql slow query log from localhost-slow.log
Count: 2 Time=7.00s (14s) Lock=0.00s (0s) Rows=0.0 (0), root[root]@localhost
select * from t_page_sample order by id desc limit N,N

自带的mysqldumpslow简单实用，作为我个人的首选。关于具体的参数含义，可以参见它自身的HELP。

2,mk-query-digest。(网上著名的开源脚本家族Maatkit中一员)

手册地址：http://www.maatkit.org/doc/mk-query-digest.html

下载方法：wget http://www.maatkit.org/get/mk-query-digest

完了赋给它可执行权限就OK。

mk-query-digest 功能太多，我今天只是试了下它对MySQL慢日志的分析功能。

以下是我觉得比较实用的功能。

1）分析慢日志并且把找出来的语句写到规定的表里。

[root@localhost ~]# ./mk-query-digest --limit 2 --select Query_time,Lock_time,Rows_sent,Rows_examined,ts --create-review-table --review D=t_girl,t=query_review localhost-slow.log
# 280ms user time, 80ms system time, 11.56M rss, 16.65M vsz
# Current date: Sat May  8 02:47:39 2010
# Files: localhost-slow.log
# Overall: 4 total, 3 unique, 0.01 QPS, 1.96x concurrency ________________
#                    total     min     max     avg     95%  stddev  median
# Exec time          1443s      5s   1418s    361s   1357s    584s    684s
# Lock time              0       0       0       0       0       0       0
# Rows sent              1       0       1    0.25    0.99    0.43       0
# Rows exam          6.98M   1.69M   1.89M   1.74M   1.86M  76.62k   1.69M
# Time range        2010-05-08 00:28:42 to 2010-05-08 00:40:58
# Profile
# Rank Query ID           Response time    Calls R/Call    Item
# ==== ================== ================ ===== ========= ===============
#    1 0x2A94F91D8C3B4B26  1418.0000 99.0%     1 1418.0000 INSERT SELECT t_page_sample
#    2 0x06754F1BD3C8D697    14.0000  1.0%     2    7.0000 SELECT t_page_sample
# Query 1: 0 QPS, 0x concurrency, ID 0x2A94F91D8C3B4B26 at byte 0 ________
# This item is included in the report because it matches --limit.
#              pct   total     min     max     avg     95%  stddev  median
# Count         25       1
# Exec time     98   1418s   1418s   1418s   1418s   1418s       0   1418s
# Lock time      0       0       0       0       0       0       0       0
# Rows sent      0       0       0       0       0       0       0       0
# Rows exam     27   1.89M   1.89M   1.89M   1.89M   1.89M       0   1.89M
# Time range 2010-05-08 00:28:42 to 2010-05-08 00:28:42
# Query_time distribution
#   1us
#  10us
# 100us
#   1ms
#  10ms
# 100ms
#    1s
#  10s+  ################################################################
# Review information
#    first_seen: 2010-05-08 00:28:42
#     last_seen: 2010-05-08 00:28:42
#   reviewed_by:
#   reviewed_on:
#      comments:
# Tables
#    SHOW TABLE STATUS FROM `t_girl` LIKE 't_page_sample'\G
#    SHOW CREATE TABLE `t_girl`.`t_page_sample`\G
insert ignore into t_page_sample select ceil(rand()*10000000), ceil(rand()*9), date_sub(now(),interval floor(rand()*20) day), now() from t_page_sample\G
# Query 2: 0.07 QPS, 0.47x concurrency, ID 0x06754F1BD3C8D697 at byte 1499
# This item is included in the report because it matches --limit.
#              pct   total     min     max     avg     95%  stddev  median
# Count         50       2
# Exec time      0     14s      5s      9s      7s      9s      3s      7s
# Lock time      0       0       0       0       0       0       0       0
# Rows sent      0       0       0       0       0       0       0       0
# Rows exam     48   3.39M   1.69M   1.69M   1.69M   1.69M       0   1.69M
# Time range 2010-05-08 00:40:28 to 2010-05-08 00:40:58
# Query_time distribution
#   1us
#  10us
# 100us
#   1ms
#  10ms
# 100ms
#    1s  ################################################################
#  10s+
# Review information
#    first_seen: 2010-05-08 00:40:28
#     last_seen: 2010-05-08 00:40:58
#   reviewed_by:
#   reviewed_on:
#      comments:
# Tables
#    SHOW TABLE STATUS FROM `t_girl` LIKE 't_page_sample'\G
#    SHOW CREATE TABLE `t_girl`.`t_page_sample`\G
# EXPLAIN
select * from t_page_sample order by id desc limit 4400000,2\G
[root@localhost ~]#

因为慢日志里面会有写和读语句，所以当以后想要分析某类语句时，只需要简单的SELECT即可出来。

mysql> select * from query_review where fingerprint like 'select%'\G
*************************** 1. row ***************************
checksum: 465365117438580375
fingerprint: select * from t_page_sample order by id desc limit ?
sample: select * from t_page_sample order by id desc limit 4400000,2
first_seen: 2010-05-08 00:40:28
last_seen: 2010-05-08 00:40:58
reviewed_by: NULL
reviewed_on: NULL
comments: NULL
1 rows in set (0.00 sec)

2. 分析当前运行的SQL语句。

以前我都是自己写脚本，配合CRONTAB来定时抓取信息到固定的文件里以备分析。不过现在可以用它来打印出比较详细的报告来。

[root@localhost ~]# ./mk-query-digest --select Query_time,Lock_time,Rows_sent,Rows_examined  --processlist h=localhost,u=root
# Caught SIGINT.
# 690ms user time, 2.4s system time, 11.27M rss, 16.41M vsz
# Current date: Sat May  8 03:17:39 2010
# Files: STDIN
# Overall: 1 total, 1 unique, 0 QPS, 0x concurrency ______________________
#                    total     min     max     avg     95%  stddev  median
# Exec time        1273313855s 1273313855s 1273313855s 1273313855s 1273313855s       0 1273313855s
# Lock time              0       0       0       0       0       0       0
# Profile
# Rank Query ID           Response time          Calls R/Call          Ite
# ==== ================== ====================== ===== =============== ===
#    1 0xB52E1970DE36E57F 1273313854.8595 100.0%     1 1273313854.8595 SELECT t_page_sample
# Query 1: 0 QPS, 0x concurrency, ID 0xB52E1970DE36E57F 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 1273313855s 1273313855s 1273313855s 1273313855s 1273313855s       0 1273313855s
# Lock time      0       0       0       0       0       0       0       0
# Query_time distribution
#   1us
#  10us
# 100us
#   1ms
#  10ms
# 100ms
#    1s
#  10s+  ################################################################
# Tables
#    SHOW TABLE STATUS FROM `t_girl` LIKE 't_page_sample'\G
#    SHOW CREATE TABLE `t_girl`.`t_page_sample`\G
# EXPLAIN
select count(*) from t_page_sample\G
[root@localhost ~]#

当想停止截取当前语句时，按住CTRL+C就OK。

不过我还是喜欢我自己的那个小脚本。哈哈。

--转自