怎么分析慢查询日志？

[root@www mysql]$ Can't determine basedir from 'my_print_defaults mysqld' output: --character-set-server=gbk
--socket=/disk/mysql/mysql.sock
--server-id=163
--log-bin=mysql-bin
--binlog-ignore-db=mysql
--binlog-do-db=qzt
--replicate-do-db=qzt
--auto_increment_offset=2
--auto_increment_increment=2
--relay-log=www-relay-bin
[root@www mysql]$

如果发现 mysqldumpslow 时输出如上信息，那是因为 /etc/my.cnf 中少了 basedir 和 datadir 配置项。

mysql> +-----------------------------------------+----------------------------+
| Variable_name                           | Value                      |
+-----------------------------------------+----------------------------+
| basedir                                 | /usr                       |
| binlog_direct_non_transactional_updates | OFF                        |
| character_sets_dir                      | /usr/share/mysql/charsets/ |
| datadir                                 | /disk/mysql/               |
| innodb_data_home_dir                    |                            |
| innodb_log_group_home_dir               | ./                         |
| innodb_max_dirty_pages_pct              | 75                         |
| lc_messages_dir                         | /usr/share/mysql/          |
| plugin_dir                              | /usr/lib/mysql/plugin/     |
| slave_load_tmpdir                       | /tmp                       |
| tmpdir                                  | /tmp                       |
+-----------------------------------------+----------------------------+
11 rows in set (0.00 sec)


mysql>

现在根据上面的目录修改 /etc/my.cnf

在 [mysqld] 一节中增加（注意要根据实际情况来改）

basedir = /usr   
datadir = /disk/mysql/