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作用
可以用来分析当前会话中的sql语句执行消耗的资源情况。默认情况下是关闭的。
开启
show variables like 'profiling';查看是否开启
set profiling=1;开启
使用
show profiles;可以查看最近使用的sql语句执行情况：
+----------+------------+---------------------------------+
| Query_ID | Duration | Query |
+----------+------------+---------------------------------+
| 1 | 0.00169300 | show variables like 'profiling' |
| 2 | 0.00014275 | select version() |
| 3 | 0.00037900 | show databases |
| 4 | 0.00015600 | SELECT DATABASE() |
| 5 | 0.00029025 | show databases |
| 6 | 0.00014450 | show tables |
| 7 | 0.00032650 | show tables |
| 8 | 0.00026725 | select * from boys |
+----------+------------+---------------------------------+
8 rows in set, 1 warning (0.00 sec)
show profile cpu,block io for query 8;查询具体的某一条sql（例如queryId为8）执行情况:
+----------------------+----------+----------+------------+--------------+---------------+
| Status | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting | 0.000077 | 0.000076 | 0.000000 | 0 | 0 |
| checking permissions | 0.000011 | 0.000010 | 0.000000 | 0 | 0 |
| Opening tables | 0.000023 | 0.000023 | 0.000000 | 0 | 0 |
| init | 0.000020 | 0.000020 | 0.000000 | 0 | 0 |
| System lock | 0.000009 | 0.000008 | 0.000000 | 0 | 0 |
| optimizing | 0.000005 | 0.000005 | 0.000000 | 0 | 0 |
| statistics | 0.000014 | 0.000014 | 0.000000 | 0 | 0 |
| preparing | 0.000011 | 0.000011 | 0.000000 | 0 | 0 |
| executing | 0.000003 | 0.000003 | 0.000000 | 0 | 0 |
| Sending data | 0.000051 | 0.000052 | 0.000000 | 0 | 0 |
| end | 0.000004 | 0.000004 | 0.000000 | 0 | 0 |
| query end | 0.000008 | 0.000007 | 0.000000 | 0 | 0 |
| closing tables | 0.000008 | 0.000008 | 0.000000 | 0 | 0 |
| freeing items | 0.000014 | 0.000014 | 0.000000 | 0 | 0 |
| cleaning up | 0.000011 | 0.000011 | 0.000000 | 0 | 0 |
+----------------------+----------+----------+------------+--------------+---------------+
15 rows in set, 1 warning (0.00 sec)
需要注意以下，status如果出现以下的字段，则需要优化：
- converting HEAP to MyISAM
- create tmp table
- copying to tmp table on disk
- locked
全局查询日志
记住不要在生产环境中使用该功能，可以选择在测试环境中使用。
开启
set global general_log=1;
set global output='TABLE';
启用之后，执行的sql语句都将会被记录在general_log表当中：
select * from mysql.general_log;
+----------------------------+---------------------------+-----------+-----------+--------------+---------------------------------+
| event_time | user_host | thread_id | server_id | command_type | argument |
+----------------------------+---------------------------+-----------+-----------+--------------+---------------------------------+
| 2020-10-08 22:35:04.993412 | root[root] @ localhost [] | 616 | 0 | Query | select * from boys |
| 2020-10-08 22:35:20.995027 | root[root] @ localhost [] | 616 | 0 | Query | select * from mysql.general_log |
+----------------------------+---------------------------+-----------+-----------+--------------+---------------------------------+
2 rows in set (0.00 sec)