mysql show profiles使用分析sql性能
Show profiles是5.0.37之後添加的，要想使用此功能，要確保版本在5.0.37之後。
查看一下我的數據庫版本
mysql> Select version();
+---------------------+
| version() |
+---------------------+
| 5.0.82-community-nt |
+---------------------+
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1 row in set (0.00 sec)
版本是支持show profiles功能的。接下來進入mysql性能跟蹤診斷的世界
查看是否打開了profiles功能,默認是關閉的
mysql> use test;
Database changed
mysql> show profiles;
Empty set (0.00 sec)
顯示為空，說明profiles功能是關閉的。下面開啟
mysql> set profiling=1;
Query OK, 0 rows affected (0.00 sec)
執行下面的查詢
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mysql> explain select distinct player_idfrom task limit 20;
mysql> select distinct player_id from task ;
然後執行 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 |
+----------+------------+------------------------------------------------------+
此時可以看到執行select distinct player_id from task 用了1.91772775秒的時間
根據query_id 查看某個查詢的詳細時間耗費
mysql> show profile for query 2;
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+----------------------+----------+
| 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 |
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| 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 |
+----------------------+----------+
可以看到紅色字體部分耗費了大量時間，這是因為distinct查看會用到臨時表
那麼可不可以查看占用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 |
+----------------------+----------+----------+------------+--------------+------
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---------+
| 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 | www.2cto.com
| 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 |
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| logging slow query | 0.000002 | NULL | NULL | NULL |
NULL |
| cleaning up | 0.000003 | NULL | NULL | NULL |
NULL |
+----------------------+----------+----------+------------+--------------+------
另外還可以看到memory,swaps,context switches,source 等信息
具體信息可以參考http://dev.mysql.com/doc/refman/5.0/en/show-profiles.html
作者 aeolus_pu
