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关于MySQL的慢日志分析工具

發布時間：2025/3/20 数据库 25 豆豆

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今天我們看看關于MySQL慢日志的閱讀。
我們知道，如果我們的語句不夠優化，那么首先MySQL的慢日志是進一步優化的離線證據，雖然里面有好多“偽慢語句”！
先不說怎么優化，如果你的日志有一條語句賭住了，那么會有不計其數的慢語句填充到MySQL的滿日志里面。那么首先提煉出這些語句就非常頭疼。
今天主要介紹兩種工具：
1,mysqldumpslow。（咱們 MySQL自帶的簡單而又實用的工具）

我們先來看下mysqldumpslow的結果。
[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語句：

[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

自帶的mysqldumpslow簡單實用，作為我個人的首選。關于具體的參數含義，可以參見它自身的HELP。

2,mk-query-digest。(網上著名的開源腳本家族Maatkit中一員)

手冊地址：http://www.maatkit.org/doc/mk-query-digest.html

下載方法：wget http://www.maatkit.org/get/mk-query-digest

完了賦給它可執行權限就OK。

mk-query-digest 功能太多，我今天只是試了下它對MySQL慢日志的分析功能。

以下是我覺得比較實用的功能。

1）分析慢日志并且把找出來的語句寫到規定的表里。
[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 ~]#

因為慢日志里面會有寫和讀語句，所以當以后想要分析某類語句時，只需要簡單的SELECT即可出來。

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. 分析當前運行的SQL語句。

以前我都是自己寫腳本，配合CRONTAB來定時抓取信息到固定的文件里以備分析。不過現在可以用它來打印出比較詳細的報告來。

[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 ~]#

當想停止截取當前語句時，按住CTRL+C就OK。

不過我還是喜歡我自己的那個小腳本。哈哈。

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