mysql show profiles 使用分析sql 性能

Show profiles是5.0.37之后添加的，要想使用此功能，要确保版本在5.0.37之后。

查看一下我的数据库版本

MySQL> Select  version();

+---------------------+

| version()           |

+---------------------+

| 5.0.82-community-nt |

+---------------------+

1 row in set (0.00 sec)

版本是支持show profiles功能的。接下来进入mysql性能跟踪诊断的世界

查看是否打开了profiles功能,默认是关闭的

mysql> use test;

Database changed

mysql> show profiles;

Empty set (0.00 sec)

显示为空，说明profiles功能是关闭的。下面开启

mysql> set profiling=1;

Query OK, 0 rows affected (0.00 sec)

执行下面的查询

mysql> explain select distinct player_idfrom task limit 20;

mysql> select distinct player_id from task ;

然后执行 show profiles

mysql> show profiles;

+----------+------------+------------------------------------------------------+

| Query_ID | Duration   | Query                                               |

+----------+------------+------------------------------------------------------+

|       1 | 0.00035225 | explain select distinct player_id from task limit 20 |

|       2 | 1.91772775 | select distinct player_id from task                  |

+----------+------------+------------------------------------------------------+

此时可以看到执行select distinct player_id from task 用了1.91772775秒的时间

根据query_id 查看某个查询的详细时间耗费

mysql> show profile for query 2;

+----------------------+----------+

| Status               | Duration |

+----------------------+----------+

| starting             | 0.000052 |

| Opening tables       | 0.000009 |

| System lock          | 0.000003 |

| Table lock           | 0.000007 |

| init                 | 0.000013 |

| optimizing           | 0.000003 |

| statistics           | 0.000009 |

| preparing            | 0.000008 |

| Creating tmp table   | 0.000074 |

| executing            | 0.000002 |

| Copying to tmp table |1.916551 |

| Sending data         | 0.000667 |

| end                  | 0.000004 |

| removing tmp table   | 0.000065 |

| end                  | 0.000002 |

| end                  | 0.000002 |

| query end            | 0.000003 |

| freeing items        | 0.000245 |

| closing tables       | 0.000006 |

| logging slow query   | 0.000002 |

| cleaning up          | 0.000003 |

+----------------------+----------+

可以看到红色字体部分耗费了大量时间，这是因为distinct查看会用到临时表

那么可不可以查看占用cpu、 io等信息呢

mysql> show profile block io,cpu for query2;

+----------------------+----------+----------+------------+--------------+------

---------+

| Status               | Duration | CPU_user |CPU_system | Block_ops_in | Block

_ops_out |

+----------------------+----------+----------+------------+--------------+------

---------+

| starting             | 0.000052 |     NULL |       NULL |         NULL |

NULL |

| Opening tables       | 0.000009 |     NULL |       NULL |         NULL |

NULL |

| System lock          | 0.000003 |     NULL |       NULL |         NULL |

NULL |

| Table lock           | 0.000007 |     NULL |       NULL |         NULL |

NULL |

| init                 | 0.000013 |     NULL |       NULL |         NULL |

NULL |

| optimizing           | 0.000003 |     NULL |       NULL |         NULL |

NULL |

| statistics           | 0.000009 |     NULL |       NULL |         NULL |

NULL |

| preparing            | 0.000008 |     NULL |       NULL |        NULL |

NULL |

| Creating tmp table   | 0.000074 |     NULL |       NULL |         NULL |

NULL |

| executing            | 0.000002 |     NULL |       NULL |         NULL |

NULL |

| Copying to tmp table | 1.916551 |     NULL |       NULL |        NULL |

NULL |

| Sending data         | 0.000667 |     NULL |       NULL |         NULL |

NULL |

| end                  | 0.000004 |     NULL |       NULL |         NULL |

NULL |

| removing tmp table   | 0.000065 |     NULL |       NULL |         NULL |

NULL |

| end                  | 0.000002 |     NULL |       NULL |         NULL |

NULL |

| end                  | 0.000002 |     NULL |       NULL |         NULL |

NULL |

| query end            | 0.000003 |     NULL |       NULL |         NULL |

NULL |

| freeing items        | 0.000245 |     NULL |       NULL |         NULL |

NULL |

| closing tables       | 0.000006 |     NULL |       NULL |         NULL |

NULL |

| logging slow query   | 0.000002 |     NULL |       NULL |         NULL |

NULL |

| cleaning up          | 0.000003 |     NULL |       NULL |         NULL |

NULL |

+----------------------+----------+----------+------------+--------------+------

另外还可以看到memory,swaps,context switches,source 等信息

具体信息可以参考http://dev.mysql.com/doc/refman/5.0/en/show-profiles.html