information_schema.profiling学习

information_schema.profiling可以用来分析每一条SQL在它执行的各个阶段的用时,注意这个表是session 级的,也就是说如果session1 开启了它;session2没有开启

这个情况下session2 去查询只会返回一个空表

 

1、set @@ssesion.profiling=1 可以开启information_schema.profiling相关监测

 

2、information_schema.profiling 表的常用列

  1、query_id              :查询id 用于标记不同的查询

  2、seq                 :一个查询内部执行的步骤

  3、state                :各个步骤的状态

  4、duration              :各个步骤持续的时间

  5、cpu_user              :用户空间的cpu 使用量

  6、cpu_system            :内核空间的cpu 使用量

  7、swaps               :swap 发生的次数

 

3、例子:

  1、开启监测

set @@ssesion.profiling=1;

  2、执行查询

select * from tempdb.t;

  3、关闭监测

set @@ssesion.profiling=0;

  4、查询监测到的数据

 select
    -> query_id, -- 查询id 它用于标识一个查询
    -> seq, -- 显示序号
    -> (select sum(duration) from information_schema.profiling as innert where innert.query_id = outert.query_id) as total_cost , -- 总用时in seconds
    -> state,-- 状态
    -> duration, -- 持续时间
    -> cpu_user, -- 用户空间的cpu 使用量
    -> cpu_system, -- 内核空间的cpu 使用量
    -> -- context_voluntary, -- 自愿上下文切换
    -> -- context_involuntary, -- 非自愿上下文切换
    -> block_ops_in, -- 块调入次数
    -> block_ops_out, -- 块调出次数
    -> swaps -- 发生swap 的次数
    -> from
    -> information_schema.profiling as outert
    -> 
    -> order by
    -> seq;
+----------+-----+------------+----------------------+----------+----------+------------+--------------+---------------+-------+
| query_id | seq | total_cost | state                | duration | cpu_user | cpu_system | block_ops_in | block_ops_out | swaps |
+----------+-----+------------+----------------------+----------+----------+------------+--------------+---------------+-------+
|        1 |   2 |   0.001984 | starting             | 0.000058 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   3 |   0.001984 | checking permissions | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   4 |   0.001984 | Opening tables       | 0.000033 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   5 |   0.001984 | init                 | 0.000018 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   6 |   0.001984 | System lock          | 0.000012 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   7 |   0.001984 | optimizing           | 0.000006 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   8 |   0.001984 | statistics           | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |   9 |   0.001984 | preparing            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  10 |   0.001984 | executing            | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  11 |   0.001984 | Sending data         | 0.000130 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  12 |   0.001984 | end                  | 0.000009 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  13 |   0.001984 | query end            | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  14 |   0.001984 | closing tables       | 0.001613 | 0.002000 |   0.000000 |            0 |             0 |     0 |
|        1 |  15 |   0.001984 | freeing items        | 0.000037 | 0.000000 |   0.000000 |            0 |             0 |     0 |
|        1 |  16 |   0.001984 | cleaning up          | 0.000020 | 0.000000 |   0.000000 |            0 |             0 |     0 |
+----------+-----+------------+----------------------+----------+----------+------------+--------------+---------------+-------+

 

posted on 2016-09-03 14:44  蒋乐兴的技术随笔  阅读(2667)  评论(0编辑  收藏

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