Mysql使用Profiling分析语句消耗

Profiling 分析具体的sql语句消耗
MySQL5.0.37版本以上支持了Profiling – 官方手册。此工具可用来查询 SQL 会执行多少时间，System lock和Table lock 花多少时间等等，对定位一条语句的 I/O消耗和CPU消耗 非常重要。
从启动profile之后的所有查询包括错误的语句都会记录。
关闭会话或者set profiling=0 就关闭了。

# 开启 profiling
mysql> set profiling=1;
mysql> select * from user limit 1;
mysql> select count(*) from user group by sexal;
# 查看这些语句的profile
mysql> show profiles;
+--------------+----------------+--------------------------------------------------------------+
| Query_ID | Duration     | Query                                                                      |
+--------------+----------------+--------------------------------------------------------------+
|        1        | 0.00013200   | SELECT DATABASE()                                               |
|        2        | 0.00044100   | select * from user limit 2                                      |
|        3        | 1.95544100   | select nick,count(*) from user group by online|
+--------------+----------------+--------------------------------------------------------------+

查看具体一条（Query_ID=3 这一条）语句的profiles，包括CPU和柱塞I/O的情况

mysql> show profile cpu,block io for query 3;
+----------------------+----------+----------+------------+--------------+---------------+
| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting             | 0.000057 | 0.000000 |   0.000000 |            0 |             0 |
| Opening tables       | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |
| System lock          | 0.000006 | 0.000000 |   0.000000 |            0 |             0 |
| Table lock           | 0.000009 | 0.000000 |   0.000000 |            0 |             0 |
| init                 | 0.000021 | 0.000000 |   0.000000 |            0 |             0 |
| optimizing           | 0.000006 | 0.000000 |   0.000000 |            0 |             0 |
| statistics           | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |
| preparing            | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |
| Creating tmp table   | 0.000039 | 0.000000 |   0.000000 |            0 |             0 |
| executing            | 0.000005 | 0.000000 |   0.000000 |            0 |             0 |
| Copying to tmp table | 1.900619 | 1.030785 |   0.197970 |          127 |           127 |
| Sorting result       | 0.000015 | 0.000000 |   0.000000 |            0 |             0 |
| Sending data         | 0.000015 | 0.000000 |   0.000000 |            0 |             0 |
| end                  | 0.000005 | 0.000000 |   0.000000 |            0 |             0 |
| removing tmp table   | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |
| end                  | 0.000005 | 0.000000 |   0.000000 |            0 |             0 |
| query end            | 0.000004 | 0.000000 |   0.000000 |            0 |             0 |
| freeing items        | 0.000025 | 0.000000 |   0.000000 |            0 |             0 |
| logging slow query   | 0.000004 | 0.000000 |   0.000000 |            0 |             0 |
| cleaning up          | 0.000005 | 0.000000 |   0.000000 |            0 |             0 |
+----------------------+----------+----------+------------+--------------+---------------+

上面就获得了一条语句的CPU和Block IO消耗，对定位瓶颈很方便，其余的一些信息，可以用语句：“Show profile *** for query 3”来获取

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