使用show profiles分析SQL性能

介绍
如何查看执行SQL的耗时的步骤：开启profile、发送sql、查看profile的资源开销结果、关闭profile。
- profile默认是不打开的
- 验证修改后的结果
- 开启profile，然后测试
- 获取profile的帮助
获取SQL语句的开销信息
需要注意的四点
全局查询日志
- 开启全局查询日志

介绍

分析SQL执行带来的开销是优化SQL的重要手段。在MySQL数据库中，可以通过配置profiling参数来启用SQL剖析。该参数可以在全局和session级别来设置。对于全局级别则作用于整个MySQL实例，而session级别紧影响当前session。该参数开启后，后续执行的SQL语句都将记录其资源开销，诸如IO，上下文切换，CPU，Memory等等。根据这些开销进一步分析当前SQL瓶颈从而进行优化与调整

如何查看执行SQL的耗时的步骤：开启profile、发送sql、查看profile的资源开销结果、关闭profile。

profile默认是不打开的

mysql> show profiles;
Empty set (0.02 sec)

验证修改后的结果

mysql> show variables like "%pro%";
可以看到profiling 默认是OFF的。

开启profile，然后测试

开启profile
mysql> set profiling=1;

获取profile的帮助

help profile;

root@localhost[dhy]> help profile;  
Name: 'SHOW PROFILE'  
Description:  
Syntax:  
SHOW PROFILE [type [, type] ... ]  
    [FOR QUERY n]  
    [LIMIT row_count [OFFSET offset]]  
  
type:  
    ALL                --显示所有的开销信息  
  | BLOCK IO           --显示块IO相关开销  
  | CONTEXT SWITCHES   --上下文切换相关开销  
  | CPU                --显示CPU相关开销信息  
  | IPC                --显示发送和接收相关开销信息  
  | MEMORY             --显示内存相关开销信息  
  | PAGE FAULTS        --显示页面错误相关开销信息  
  | SOURCE             --显示和Source_function，Source_file，Source_line相关的开销信息  
  | SWAPS              --显示交换次数相关开销的信息   
  
The SHOW PROFILE and SHOW PROFILES statements display profiling  
information that indicates resource usage for statements executed  
during the course of the current session.  
  
*Note*: These statements are deprecated as of MySQL 5.6.7 and will be  
removed in a future MySQL release. Use the Performance Schema instead;  
see http://dev.mysql.com/doc/refman/5.6/en/performance-schema.html.  
--上面描述从5.6.7开始该命令将会被移除，用Performance Schema instead代替  
--在Oracle数据库中，是通过autotrace来剖析单条SQL并获取真实的执行计划以及其开销信息

执行业务SQL，并用profile分析示例：

--发布SQL查询  
root@localhost[dhy]> select count(*) from customer;  
+----------+  
| count(*) |  
+----------+  
|      599 |  
+----------+  
  
--查看当前session所有已产生的profile  
root@localhost[dhy]> show profiles;  
+----------+------------+--------------------------------+  
| Query_ID | Duration   | Query                          |  
+----------+------------+--------------------------------+  
|        1 | 0.00253600 | show variables like '%profil%' |  
|        2 | 0.00138150 | select count(*) from customer  |  
+----------+------------+--------------------------------+  
2 rows in set, 1 warning (0.01 sec)  
  
--我们看到有2个warning，之前一个，现在一个  
root@localhost[dhy]> show warnings;    --下面的结果表明SHOW PROFILES将来会被Performance Schema替换掉  
+---------+------+--------------------------------------------------------------------------------------------------------------+  
| Level   | Code | Message                                                                                                      |  
+---------+------+--------------------------------------------------------------------------------------------------------------+  
| Warning | 1287 | 'SHOW PROFILES' is deprecated and will be removed in a future release. Please use Performance Schema instead |  
+---------+------+--------------------------------------------------------------------------------------------------------------+

获取SQL语句的开销信息

–可以直接使用show profile来查看上一条SQL语句的开销信息
–注，show profile之类的语句不会被profiling，即自身不会产生Profiling
–我们下面的这个show profile查看的是show warnings产生的相应开销

root@localhost[dhy]> show profile;    
+----------------+----------+  
| Status         | Duration |  
+----------------+----------+  
| starting       | 0.000141 |  
| query end      | 0.000058 |  
| closing tables | 0.000014 |  
| freeing items  | 0.001802 |  
| cleaning up    | 0.000272 |  
+----------------+----------+

--如下面的查询show warnings被添加到profiles  
root@localhost[sakila]> show profiles;  
+----------+------------+--------------------------------+  
| Query_ID | Duration   | Query                          |  
+----------+------------+--------------------------------+  
|        1 | 0.00253600 | show variables like '%profil%' |  
|        2 | 0.00138150 | select count(*) from customer  |  
|        3 | 0.00228600 | show warnings                  |  
+----------+------------+--------------------------------+  
  
--获取指定查询的开销（第二条查询的开销明细） 
root@localhost[sakila]> show profile for query 2;  
+----------------------+----------+  
| Status               | Duration |  
+----------------------+----------+  
| starting             | 0.000148 |  
| checking permissions | 0.000014 |  
| Opening tables       | 0.000047 |  
| init                 | 0.000023 |  
| System lock          | 0.000035 |  
| optimizing           | 0.000012 |  
| statistics           | 0.000019 |  
| preparing            | 0.000014 |  
| executing            | 0.000006 |  
| Sending data         | 0.000990 |  
| end                  | 0.000010 |  
| query end            | 0.000011 |  
| closing tables       | 0.000010 |  
| freeing items        | 0.000016 |  
| cleaning up          | 0.000029 |  
+----------------------+----------+  
  
--查看特定部分的开销，如下为CPU部分的开销  
root@localhost[sakila]> show profile cpu for query 2 ;  
+----------------------+----------+----------+------------+  
| Status               | Duration | CPU_user | CPU_system |  
+----------------------+----------+----------+------------+  
| starting             | 0.000148 | 0.000000 |   0.000000 |  
| checking permissions | 0.000014 | 0.000000 |   0.000000 |  
| Opening tables       | 0.000047 | 0.000000 |   0.000000 |  
| init                 | 0.000023 | 0.000000 |   0.000000 |  
| System lock          | 0.000035 | 0.000000 |   0.000000 |  
| optimizing           | 0.000012 | 0.000000 |   0.000000 |  
| statistics           | 0.000019 | 0.000000 |   0.000000 |  
| preparing            | 0.000014 | 0.000000 |   0.000000 |  
| executing            | 0.000006 | 0.000000 |   0.000000 |  
| Sending data         | 0.000990 | 0.001000 |   0.000000 |  
| end                  | 0.000010 | 0.000000 |   0.000000 |  
| query end            | 0.000011 | 0.000000 |   0.000000 |  
| closing tables       | 0.000010 | 0.000000 |   0.000000 |  
| freeing items        | 0.000016 | 0.000000 |   0.000000 |  
| cleaning up          | 0.000029 | 0.000000 |   0.000000 |  
+----------------------+----------+----------+------------+  
  
--如下为MEMORY部分的开销  
root@localhost[sakila]> show profile memory for query 2 ;  
+----------------------+----------+  
| Status               | Duration |  
+----------------------+----------+  
| starting             | 0.000148 |  
| checking permissions | 0.000014 |  
| Opening tables       | 0.000047 |  
| init                 | 0.000023 |  
| System lock          | 0.000035 |  
| optimizing           | 0.000012 |  
| statistics           | 0.000019 |  
| preparing            | 0.000014 |  
| executing            | 0.000006 |  
| Sending data         | 0.000990 |  
| end                  | 0.000010 |  
| query end            | 0.000011 |  
| closing tables       | 0.000010 |  
| freeing items        | 0.000016 |  
| cleaning up          | 0.000029 |  
+----------------------+----------+  
  
--同时查看不同资源开销  
root@localhost[sakila]> show profile block io,cpu for query 2;  
+----------------------+----------+----------+------------+--------------+---------------+  
| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |  
+----------------------+----------+----------+------------+--------------+---------------+  
| starting             | 0.000148 | 0.000000 |   0.000000 |            0 |             0 |  
| checking permissions | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |  
| Opening tables       | 0.000047 | 0.000000 |   0.000000 |            0 |             0 |  
| init                 | 0.000023 | 0.000000 |   0.000000 |            0 |             0 |  
| System lock          | 0.000035 | 0.000000 |   0.000000 |            0 |             0 |  
| optimizing           | 0.000012 | 0.000000 |   0.000000 |            0 |             0 |  
| statistics           | 0.000019 | 0.000000 |   0.000000 |            0 |             0 |  
| preparing            | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |  
| executing            | 0.000006 | 0.000000 |   0.000000 |            0 |             0 |  
| Sending data         | 0.000990 | 0.001000 |   0.000000 |            0 |             0 |  
| end                  | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |  
| query end            | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |  
| closing tables       | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |  
| freeing items        | 0.000016 | 0.000000 |   0.000000 |            0 |             0 |  
| cleaning up          | 0.000029 | 0.000000 |   0.000000 |            0 |             0 |  
+----------------------+----------+----------+------------+--------------+---------------+  
  
--下面的SQL语句用于查询query_id为2的SQL开销，且按最大耗用时间倒序排列  
root@localhost[sakila]> set @query_id=2;  
  
root@localhost[sakila]> SELECT STATE, SUM(DURATION) AS Total_R,  
    ->   ROUND(  
    ->        100 * SUM(DURATION) /  
    ->           (SELECT SUM(DURATION)  
    ->            FROM INFORMATION_SCHEMA.PROFILING  
    ->            WHERE QUERY_ID = @query_id  
    ->        ), 2) AS Pct_R,  
    ->     COUNT(*) AS Calls,  
    ->     SUM(DURATION) / COUNT(*) AS "R/Call"  
    ->  FROM INFORMATION_SCHEMA.PROFILING  
    ->  WHERE QUERY_ID = @query_id  
    ->  GROUP BY STATE  
    ->  ORDER BY Total_R DESC;  
+----------------------+----------+-------+-------+--------------+  
| STATE                | Total_R  | Pct_R | Calls | R/Call       |  
+----------------------+----------+-------+-------+--------------+  
| Sending data         | 0.000990 | 71.53 |     1 | 0.0009900000 |--最大耗用时间部分为发送数据  
| starting             | 0.000148 | 10.69 |     1 | 0.0001480000 |  
| Opening tables       | 0.000047 |  3.40 |     1 | 0.0000470000 |  
| System lock          | 0.000035 |  2.53 |     1 | 0.0000350000 |  
| cleaning up          | 0.000029 |  2.10 |     1 | 0.0000290000 |  
| init                 | 0.000023 |  1.66 |     1 | 0.0000230000 |  
| statistics           | 0.000019 |  1.37 |     1 | 0.0000190000 |  
| freeing items        | 0.000016 |  1.16 |     1 | 0.0000160000 |  
| preparing            | 0.000014 |  1.01 |     1 | 0.0000140000 |  
| checking permissions | 0.000014 |  1.01 |     1 | 0.0000140000 |  
| optimizing           | 0.000012 |  0.87 |     1 | 0.0000120000 |  
| query end            | 0.000011 |  0.79 |     1 | 0.0000110000 |  
| end                  | 0.000010 |  0.72 |     1 | 0.0000100000 |  
| closing tables       | 0.000010 |  0.72 |     1 | 0.0000100000 |  
| executing            | 0.000006 |  0.43 |     1 | 0.0000060000 |  
+----------------------+----------+-------+-------+--------------+  
  
--开启profiling后，我们可以通过show profile等方式查看，其实质是这些开销信息被记录到information_schema.profiling表  
--如下面的查询，部分信息省略  
profiling  
root@localhost[information_schema]> select * from profiling limit 3,3\G;  
*************************** 1. row ***************************  
           QUERY_ID: 1  
                SEQ: 5  
              STATE: init  
           DURATION: 0.000020  
           CPU_USER: 0.000000  
         CPU_SYSTEM: 0.000000  
  CONTEXT_VOLUNTARY: 0  
CONTEXT_INVOLUNTARY: 0  
       BLOCK_OPS_IN: 0  
      BLOCK_OPS_OUT: 0  
      MESSAGES_SENT: 0  
  MESSAGES_RECEIVED: 0  
  PAGE_FAULTS_MAJOR: 0  
  PAGE_FAULTS_MINOR: 0  
              SWAPS: 0  
    SOURCE_FUNCTION: mysql_prepare_select  
        SOURCE_FILE: sql_select.cc  
        SOURCE_LINE: 1050  
  
--停止profile,可以设置profiling参数，或者在session退出之后,profiling会被自动关闭  
root@localhost[sakila]> set profiling=off;  
Query OK, 0 rows affected, 1 warning (0.00 sec)

需要注意的四点

converting HEAP to MyISAM 查询结果天大，内存不够用了往磁盘上般
Creating tmp table 创建临时表—拷贝数据到临时表，用完在删除
Copying to tmp table on disk 把内存中临时表复制到磁盘上
locked

全局查询日志

开启全局查询日志

修改配置文件:

在mysql的my.cnf中，设置如下:
#开启
general_log=1
#记录日志文件的路径
general_log_file=/path/logfile
#输出格式
log_output=FILE

编码启用

set global general_log=1;
#以表的形式输出
set global log_output='TABLE';

此后，编写的sql语句，将会记录到mysql的general_log表中，可以用下面的命令查看

select * from mysql.general_log;

不要在生成环境开启该功能

MySQL：使用show profiles分析SQL性能