[MySQL] 啟用query log 與 slow query log功能

本文转载地址：http://blog.permastyle.com/2010/12/mysql-%E5%95%9F%E7%94%A8query-log-%E8%88%87-slow-query-log%E5%8A%9F%E8%83%BD.html

以下範例試用在Centos 5.x，MySQL 5.0環境下

啟用query log功能
以drupal的資料庫連結多，開啟此功能，可預期query log檔案很快就變會很大，建議debug問題時才開啟。

1. $vi /etc/my.cnf

在[mysqld]區塊內設定加入

[mysqld] log=/var/log/mysqld.general.log
2. mysql不會自動依設定產生mysqld.general.log，要手動加。
$ touch /var/log/mysqld.general.log
$ chown mysql.mysql /var/log/mysqld.general.log
3. 重新啟動mysqld，用瀏覧器連結網站，查看是否有產出log資料
$ /etc/init.d/mysqld restart $
tail -f /var/log/mysqld.general.log

log資料

2 Query SELECT * FROM languages　ORDER BY weight ASC, name ASC 2 Query SELECT data, created, headers, expire, serialized FROM cache WHERE cid = 'variables:zh-hant'
2 Query SELECT COUNT(pid) FROM url_alias 2
Query SELECT src FROM url_alias WHERE dst = 'node' AND language IN('zh-hant', '') ORDER BY language DESC, pid DESC

啟用slow query log功能

1. $ vi /etc/my.cnf

在[mysqld]區塊內設定加入
5.0版

[mysqld] // 單位是秒，預設是10秒，最小值是1
 log-slow-queries = 5
 log-slow-queries = /var/log/mysql-slow.log
 log-long-format

5.1.29版後

[mysqld]
slow_query_log
slow_query_log_file = /var/log/mysql-slow.log
long_query_time = 5
log-long-format
2. mysql不會自動依設定產生mysql-slow.log，要手動加。
$ touch /var/log/mysql-slow.log
$ chown mysql.mysql /var/log/mysql-slow.log
3. 重新啟動mysqld，用瀏覧器連結網站，查看是否有產出log資料
$ /etc/init.d/mysqld restart $ tail -f /var/log/mysql-slow.log

log資料

# Time: 090317 18:46:59
# User@Host: root[root] @ localhost [] # Query_time: 12 Lock_time: 0 Rows_sent: 242515 Rows_examined: 242515 SELECT * FROM `portal`.`search_index`;

使用mysqldumpslow 指令分析mysql-slow.log，結果是耗費最多時間的slow query依順排出。

// query 7次，每次耗費106.43秒 Count: 7 Time=106.43s (745s) Lock=0.00s (0s) Rows=9366.9 (65568), aaa[aaa]@localhost SELECT * FROM `aaa`.`vtiger_crmentity` // query 1次，每次耗費58.00秒 Count: 1 Time=58.00s (58s) Lock=0.00s (0s) Rows=51515.0 (51515), aaa[aaa]@localhost SELECT * FROM `aaa`.`product_mac2` Count: 1 Time=42.00s (42s) Lock=0.00s (0s) Rows=1000.0 (1000), aaa[aaa]@[215.86.72.122] SELECT * FROM aaa.product_mac2 LIMIT N Count: 6 Time=38.00s (228s) Lock=0.00s (0s) Rows=130972.3 (785834), aaa[aaa]@localhost SELECT * FROM `aaa`.`vtiger_audit_trial`