Mysql SQL优化工具我们常使用explain去解析sql的执行，根据执行计划去评估sql的性能消耗瓶颈，而MYSQL Profiling提供我们详细的SQL执行过程中的cpu/io/swap/memory等使用情况以及每个过程执行时间消耗。
主要用途为1：查看SQL执行消耗瓶颈位置2、查看sql的执行过程，每步操作在具体哪个源码文件的什么位置
这里简单介绍下其使用方式：
profiling在mysql 5.0.37版本以后支持，在mysql5.7后可以通过performance_schema替代（25.18.1 Query Profiling Using Performance Schema），但通过session级别的追踪比较方便
1、相关变量
(root:localhost:Wed Nov 15 16:32:50 2017)[performance_schema]> show variables like '%profil%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| have_profiling | YES | ##是否支持profile功能
| profiling | ON | ##是否开启profile ，0|off表示关闭，1|on表示开启
| profiling_history_size | 15 | ##展示的历史sql数，默认是最近的15条，最大值是100
+------------------------+-------+
2、查看语法
可以通过help show profiles查看帮助文档
show profiles可以查看历史执行最近的15条sql

点击(此处)折叠或打开

SHOW PROFILE [type [, type] ... ]

[FOR QUERY n]

[LIMIT row_count [OFFSET offset]]

type:

ALL

| BLOCK IO

| CONTEXT SWITCHES

| CPU

| IPC

| MEMORY

| PAGE FAULTS

| SOURCE

| SWAPS

3、使用实例
1）开启profling
(root:localhost:Wed Nov 15 16:37:00 2017)[dbtest]> set profiling=1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

(root:localhost:Wed Nov 15 16:37:14 2017)[dbtest]> show variables like '%profil%';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| have_profiling | YES |
| profiling | ON |
| profiling_history_size | 15 |
+------------------------+-------+
3 rows in set (0.00 sec)
2）查看所有profiling记录的sql
(root:localhost:Wed Nov 15 16:37:16 2017)[dbtest]> show profiles;
+----------+------------+--------------------------------+
| Query_ID | Duration | Query |
+----------+------------+--------------------------------+
| 1 | 0.00089900 | show variables like '%profil%' |
+----------+------------+--------------------------------+
3）查看指定profiling记录的sql
(root:localhost:Wed Nov 15 16:39:14 2017)[dbtest]> show profile for query 2 ;
+----------------------+----------+
| Status | Duration |
+----------------------+----------+
| starting | 0.000103 |
| checking permissions | 0.000008 |
| Opening tables | 0.000060 |
| init | 0.000023 |
| System lock | 0.000011 |
| optimizing | 0.000007 |
| statistics | 0.000016 |
| preparing | 0.000015 |
| executing | 0.000007 |
| Sending data | 0.000063 |
| end | 0.000004 |
| query end | 0.000010 |
| closing tables | 0.000012 |
| freeing items | 0.000016 |
| logging slow query | 0.000003 |
| logging slow query | 0.000070 |
| cleaning up | 0.000014 |
+----------------------+----------+
4）查看指定profiling记录的sql，并且显示cpu/block io/的步骤消耗信息

(root:localhost:Wed Nov 15 16:43:47 2017)[dbtest]> show profile cpu ,block io for query 2;
+----------------------+----------+----------+------------+--------------+---------------+
| Status | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting | 0.000103 | NULL | NULL | NULL | NULL |
| checking permissions | 0.000008 | NULL | NULL | NULL | NULL |
| Opening tables | 0.000060 | NULL | NULL | NULL | NULL |
| init | 0.000023 | NULL | NULL | NULL | NULL |
| System lock | 0.000011 | NULL | NULL | NULL | NULL |
| optimizing | 0.000007 | NULL | NULL | NULL | NULL |
| statistics | 0.000016 | NULL | NULL | NULL | NULL |
| preparing | 0.000015 | NULL | NULL | NULL | NULL |
| executing | 0.000007 | NULL | NULL | NULL | NULL |
| Sending data | 0.000063 | NULL | NULL | NULL | NULL |
| end | 0.000004 | NULL | NULL | NULL | NULL |
| query end | 0.000010 | NULL | NULL | NULL | NULL |
| closing tables | 0.000012 | NULL | NULL | NULL | NULL |
| freeing items | 0.000016 | NULL | NULL | NULL | NULL |
| logging slow query | 0.000003 | NULL | NULL | NULL | NULL |
| logging slow query | 0.000070 | NULL | NULL | NULL | NULL |
| cleaning up | 0.000014 | NULL | NULL | NULL | NULL |
+----------------------+----------+----------+------------+--------------+---------------+

5）查看指定profiling记录的sql，并且显示每步源码文件信息
(root:localhost:Wed Nov 15 16:44:09 2017)[dbtest]> show profile source for query 2;
+----------------------+----------+-----------------------+------------------+-------------+
| Status | Duration | Source_function | Source_file | Source_line |
+----------------------+----------+-----------------------+------------------+-------------+
| starting | 0.000103 | NULL | NULL | NULL |
| checking permissions | 0.000008 | check_access | sql_parse.cc | 5635 |
| Opening tables | 0.000060 | open_tables | sql_base.cc | 5029 |
| init | 0.000023 | mysql_prepare_select | sql_select.cc | 1051 |
| System lock | 0.000011 | mysql_lock_tables | lock.cc | 304 |
| optimizing | 0.000007 | optimize | sql_optimizer.cc | 138 |
| statistics | 0.000016 | optimize | sql_optimizer.cc | 381 |
| preparing | 0.000015 | optimize | sql_optimizer.cc | 504 |
| executing | 0.000007 | exec | sql_executor.cc | 110 |
| Sending data | 0.000063 | exec | sql_executor.cc | 187 |
| end | 0.000004 | mysql_execute_select | sql_select.cc | 1106 |
| query end | 0.000010 | mysql_execute_command | sql_parse.cc | 5307 |
| closing tables | 0.000012 | mysql_execute_command | sql_parse.cc | 5383 |
| freeing items | 0.000016 | mysql_parse | sql_parse.cc | 6676 |
| logging slow query | 0.000003 | log_slow_do | sql_parse.cc | 2077 |
| logging slow query | 0.000070 | log_slow_do | sql_parse.cc | 2078 |
| cleaning up | 0.000014 | dispatch_command | sql_parse.cc | 1878 |
+----------------------+----------+-----------------------+------------------+-------------+
17 rows in set, 1 warning (0.00 sec)

6）查看指定profiling记录的sql，并且显示所有的步骤消耗信息
(root:localhost:Wed Nov 15 16:40:34 2017)[dbtest]> show profile all for query 2 \G
*************************** 1. row ***************************
Status: starting
Duration: 0.000103
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: NULL
Source_file: NULL
Source_line: NULL
*************************** 2. row ***************************
Status: checking permissions
Duration: 0.000008
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: check_access
Source_file: sql_parse.cc
Source_line: 5635
*************************** 3. row ***************************
Status: Opening tables
Duration: 0.000060
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: open_tables
Source_file: sql_base.cc
Source_line: 5029
*************************** 4. row ***************************
Status: init
Duration: 0.000023
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_prepare_select
Source_file: sql_select.cc
Source_line: 1051
*************************** 5. row ***************************
Status: System lock
Duration: 0.000011
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_lock_tables
Source_file: lock.cc
Source_line: 304
*************************** 6. row ***************************
Status: optimizing
Duration: 0.000007
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: optimize
Source_file: sql_optimizer.cc
Source_line: 138
*************************** 7. row ***************************
Status: statistics
Duration: 0.000016
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: optimize
Source_file: sql_optimizer.cc
Source_line: 381
*************************** 8. row ***************************
Status: preparing
Duration: 0.000015
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: optimize
Source_file: sql_optimizer.cc
Source_line: 504
*************************** 9. row ***************************
Status: executing
Duration: 0.000007
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: exec
Source_file: sql_executor.cc
Source_line: 110
*************************** 10. row ***************************
Status: Sending data
Duration: 0.000063
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: exec
Source_file: sql_executor.cc
Source_line: 187
*************************** 11. row ***************************
Status: end
Duration: 0.000004
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_execute_select
Source_file: sql_select.cc
Source_line: 1106
*************************** 12. row ***************************
Status: query end
Duration: 0.000010
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_execute_command
Source_file: sql_parse.cc
Source_line: 5307
*************************** 13. row ***************************
Status: closing tables
Duration: 0.000012
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_execute_command
Source_file: sql_parse.cc
Source_line: 5383
*************************** 14. row ***************************
Status: freeing items
Duration: 0.000016
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: mysql_parse
Source_file: sql_parse.cc
Source_line: 6676
*************************** 15. row ***************************
Status: logging slow query
Duration: 0.000003
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: log_slow_do
Source_file: sql_parse.cc
Source_line: 2077
*************************** 16. row ***************************
Status: logging slow query
Duration: 0.000070
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: log_slow_do
Source_file: sql_parse.cc
Source_line: 2078
*************************** 17. row ***************************
Status: cleaning up
Duration: 0.000014
CPU_user: NULL
CPU_system: NULL
Context_voluntary: NULL
Context_involuntary: NULL
Block_ops_in: NULL
Block_ops_out: NULL
Messages_sent: NULL
Messages_received: NULL
Page_faults_major: NULL
Page_faults_minor: NULL
Swaps: NULL
Source_function: dispatch_command
Source_file: sql_parse.cc
Source_line: 1878
17 rows in set, 1 warning (0.00 sec)