--mysql的profile可用于查看一个sql的具体消耗
show profile all for query 1\G;

--profiling has a default value of 0 (OFF)
mysql> SELECT @@profiling;
+-------------+
| @@profiling |
+-------------+
|           0 |
+-------------+

mysql> SET profiling = 1;


--profile 的查询id可能通过如下sql找到
mysql> show profiles;      
+----------+-------------+-------------------------+
| Query_ID | Duration    | Query                   |
+----------+-------------+-------------------------+
|        1 |  0.03872950 | select count(*) from t1 |
|        2 | 10.93732000 | select count(*) from t2 |

-- 变量 profiling_history_size 记录了保存profile记录的条数
mysql> select @@profiling_history_size;
+--------------------------+
| @@profiling_history_size |
+--------------------------+
|                       15 |
+--------------------------+

MariaDB [test]> show profile all for query 1\G;
*************************** 1. row ***************************
             Status: starting
           Duration: 0.000080
           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: NULL
        Source_file: NULL
        Source_line: NULL
*************************** 2. row ***************************
             Status: checking permissions
           Duration: 0.000008
           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: check_access
        Source_file: sql_parse.cc
        Source_line: 6051
		

--在mysql5.7之后，profile信息将逐渐被废弃，mysql推荐使用performance schema
--setup_actors用于记录哪些信息会被记录
As of MySQL 5.7.8, the setup_actors table can be used to limit the collection of historical events by host, user, or account to reduce runtime overhead and the amount of data collected in history tables
mysql> SELECT * FROM performance_schema.setup_actors; 
+------+------+------+---------+---------+
| HOST | USER | ROLE | ENABLED | HISTORY |
+------+------+------+---------+---------+
| %    | %    | %    | YES     | YES     |
+------+------+------+---------+---------+		

--当然也可以修改它
UPDATE performance_schema.setup_actors SET ENABLED = 'NO', HISTORY = 'NO' WHERE HOST = '%' AND USER = '%';
INSERT INTO performance_schema.setup_actors (HOST,USER,ROLE,ENABLED,HISTORY) VALUES('localhost','test_user','%','YES','YES');

--其中还有一些初始化的表，具体信息请参阅mysql官方文档
mysql> SELECT table_schema,table_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE 'setup%' and table_schema='performance_schema';  
+--------------------+-------------------+
| table_schema       | table_name        |
+--------------------+-------------------+
| performance_schema | setup_actors      |
| performance_schema | setup_consumers   |
| performance_schema | setup_instruments |
| performance_schema | setup_objects     |
| performance_schema | setup_timers      |
+--------------------+-------------------+
5 rows in set (0.00 sec)

--开启以下性能记录
 UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES' WHERE NAME LIKE '%statement/%';
 UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES' WHERE NAME LIKE '%stage/%';
 UPDATE performance_schema.setup_consumers SET ENABLED = 'YES' WHERE NAME LIKE '%events_statements_%';
 UPDATE performance_schema.setup_consumers SET ENABLED = 'YES' WHERE NAME LIKE '%events_stages_%';

--查看指定sql的event_id
mysql> SELECT EVENT_ID, TRUNCATE(TIMER_WAIT/1000000000000,6) as Duration, SQL_TEXT FROM performance_schema.events_statements_history_long WHERE SQL_TEXT like '%select count(*) from t1%';
+----------+----------+-------------------------+
| EVENT_ID | Duration | SQL_TEXT                |
+----------+----------+-------------------------+
|       78 | 0.022121 | select count(*) from t1 |
+----------+----------+-------------------------+

--查看sql消耗如下：
mysql> SELECT event_name AS Stage, TRUNCATE(TIMER_WAIT/1000000000000,6) AS Duration FROM performance_schema.events_stages_history_long WHERE NESTING_EVENT_ID=78; 
+--------------------------------+----------+
| Stage                          | Duration |
+--------------------------------+----------+
| stage/sql/starting             | 0.000093 |
| stage/sql/checking permissions | 0.000007 |
| stage/sql/Opening tables       | 0.000024 |
| stage/sql/init                 | 0.000018 |
| stage/sql/System lock          | 0.000013 |
| stage/sql/optimizing           | 0.021755 |
| stage/sql/executing            | 0.000015 |
| stage/sql/end                  | 0.000004 |
| stage/sql/query end            | 0.000016 |
| stage/sql/closing tables       | 0.000015 |
| stage/sql/freeing items        | 0.000153 |
| stage/sql/cleaning up          | 0.000001 |
+--------------------------------+----------+