2012/04/24 11:08
文章作者:Enjoy 转载请注明原文链接。
MYSQL的profiling功能要在Mysql版本5.0.37以上才能使用。开启profiling:
set profiling=1;
查看是否设置生效:
select @@profiling;
默认是0,设置成功是1
运行SQL语句:
mysql> select * FROM hx_line WHERE id = '1455023';
查看profiles
mysql> show profiles;
+----------+------------+---------------------------------------------+
| Query_ID | Duration | Query |
+----------+------------+---------------------------------------------+
| 1 | 0.00036150 | select * FROM hx_line WHERE id = '1455023' |
+----------+------------+---------------------------------------------+
查看具体某条的profile
mysql> show profile FOR QUERY 1;
+--------------------------------+----------+
| Status | Duration |
+--------------------------------+----------+
| starting | 0.000013 |
| Waiting for query cache lock | 0.000014 |
| checking query cache for query | 0.000038 |
| checking permissions | 0.000006 |
| Opening tables | 0.000013 |
| System lock | 0.000009 |
| Waiting for query cache lock | 0.000024 |
| init | 0.000060 |
| optimizing | 0.000014 |
| statistics | 0.000046 |
| preparing | 0.000017 |
| executing | 0.000004 |
| Sending data | 0.000081 |
| end | 0.000005 |
| query end | 0.000004 |
| closing tables | 0.000008 |
| freeing items | 0.000009 |
| Waiting for query cache lock | 0.000003 |
| freeing items | 0.000013 |
| Waiting for query cache lock | 0.000003 |
| freeing items | 0.000003 |
| storing result in query cache | 0.000005 |
| logging slow query | 0.000003 |
| cleaning up | 0.000004 |
+--------------------------------+----------+
24 rows
我们看到了一个简单的查询,MYSQL内部做了24次操作。
另外,看到了一堆query cache的操作,试着把query_cache_size=0,把query_cache关闭,再次测试:
mysql> show profile FOR QUERY 1;
+----------------------+----------+
| Status | Duration |
+----------------------+----------+
| starting | 0.000040 |
| checking permissions | 0.000007 |
| Opening tables | 0.000015 |
| System lock | 0.000010 |
| init | 0.000061 |
| optimizing | 0.000013 |
| statistics | 0.000059 |
| preparing | 0.000018 |
| executing | 0.000004 |
| Sending data | 0.000092 |
| end | 0.000006 |
| query end | 0.000004 |
| closing tables | 0.000008 |
| freeing items | 0.000020 |
| logging slow query | 0.000003 |
| cleaning up | 0.000004 |
+----------------------+----------+
16 rows in set (0.00 sec)
当开启了query_cache的情况下,需要多操作6次,在这个示例里面多化了0.000087s。
查询这条语句对CPU的使用情况:
mysql> show profile cpu FOR QUERY 1;
+----------------------+----------+----------+------------+
| Status | Duration | CPU_user | CPU_system |
+----------------------+----------+----------+------------+
| starting | 0.000037 | 0.000000 | 0.000000 |
| checking permissions | 0.000009 | 0.000000 | 0.000000 |
| Opening tables | 0.000014 | 0.000000 | 0.000000 |
| System lock | 0.000009 | 0.000000 | 0.000000 |
| init | 0.000059 | 0.000000 | 0.000000 |
| optimizing | 0.000009 | 0.000000 | 0.000000 |
| statistics | 0.000044 | 0.000000 | 0.000000 |
| preparing | 0.000015 | 0.000000 | 0.000000 |
| executing | 0.000004 | 0.000000 | 0.000000 |
| Sending data | 0.000081 | 0.000000 | 0.000000 |
| end | 0.000006 | 0.000000 | 0.000000 |
| query end | 0.000004 | 0.000000 | 0.000000 |
| closing tables | 0.000008 | 0.000000 | 0.000000 |
| freeing items | 0.000021 | 0.000000 | 0.000000 |
| logging slow query | 0.000004 | 0.000000 | 0.000000 |
| cleaning up | 0.000004 | 0.000000 | 0.000000 |
+----------------------+----------+----------+------------+
show profile额外一些命令:
* ALL - displays all information
* BLOCK IO - displays counts for block input and output Operations
* CONTEXT SWITCHES - displays counts for voluntary and involuntary context switches
* ipC - displays counts for messages sent and received
* MEMORY - is not currently implemented
* PAGE FAULTS - displays counts for major and minor page faults
* SOURCE - displays the names of functions from the source code, together with the name and line number of the file in which the function occurs
* SWAPS - displays swap counts