mysql监测SQL执行时消耗资源情况

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#mysql #show profile #监控

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本文介绍如何使用MySQL的PROFILE功能来评估SQL查询的性能，并提供具体的步骤和实例，帮助读者了解SQL执行过程中的各项成本。

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使用mysql的PROFILE功能我们可以查看一个SQL执行的代价是什么情况，PROFILE功能只能在SESSION级别使用，所以我们可以根据以下SQL来进行查询：

mysql> SELECT @@profiling;
+-------------+
| @@profiling |
+-------------+
|           0 |
+-------------+
1 row in set

mysql> SET profiling = 1;
Query OK, 0 rows affected

mysql> select * from ab_test;
#查询的数据 由于条数太多 我删除了

mysql> show profiles;
+----------+----------+-----------------------+
| Query_ID | Duration | Query                 |
+----------+----------+-----------------------+
|        1 | 0.032328 | select * from ab_test |
+----------+----------+-----------------------+
1 row in set

mysql> SHOW PROFILE;
+----------------------+----------+
| Status               | Duration |
+----------------------+----------+
| starting             | 0.005237 |
| checking permissions | 0.001638 |
| Opening tables       | 0.006219 |
| init                 | 0.001662 |
| System lock          | 0.001489 |
| optimizing           | 0.001576 |
| statistics           | 0.001422 |
| preparing            | 0.001285 |
| executing            | 0.001313 |
| Sending data         | 0.001618 |
| end                  | 0.001362 |
| query end            | 0.001569 |
| closing tables       | 0.001689 |
| freeing items        | 0.002667 |
| cleaning up          | 0.001585 |
+----------------------+----------+
15 rows in set

mysql> SHOW PROFILE FOR QUERY 1;
+----------------------+----------+
| Status               | Duration |
+----------------------+----------+
| starting             | 0.005237 |
| checking permissions | 0.001638 |
| Opening tables       | 0.006219 |
| init                 | 0.001662 |
| System lock          | 0.001489 |
| optimizing           | 0.001576 |
| statistics           | 0.001422 |
| preparing            | 0.001285 |
| executing            | 0.001313 |
| Sending data         | 0.001618 |
| end                  | 0.001362 |
| query end            | 0.001569 |
| closing tables       | 0.001689 |
| freeing items        | 0.002667 |
| cleaning up          | 0.001585 |
+----------------------+----------+
15 rows in set

mysql> SHOW PROFILE CPU
 FOR QUERY 1;
+----------------------+----------+----------+------------+
| Status               | Duration | CPU_user | CPU_system |
+----------------------+----------+----------+------------+
| starting             | 0.005237 | 0.005    | 0          |
| checking permissions | 0.001638 | 0        | 0.002999   |
| Opening tables       | 0.006219 | 0.006999 | 0          |
| init                 | 0.001662 | 0.000999 | 0.001      |
| System lock          | 0.001489 | 0        | 0.001      |
| optimizing           | 0.001576 | 0        | 0.002      |
| statistics           | 0.001422 | 0        | 0.000999   |
| preparing            | 0.001285 | 0        | 0.003      |
| executing            | 0.001313 | 0        | 0          |
| Sending data         | 0.001618 | 0        | 0.002      |
| end                  | 0.001362 | 0        | 0.001      |
| query end            | 0.001569 | 0        | 0.001999   |
| closing tables       | 0.001689 | 0.003    | 0          |
| freeing items        | 0.002667 | 0.002999 | 0.001      |
| cleaning up          | 0.001585 | 0        | 0.001      |
+----------------------+----------+----------+------------+
15 rows in set
mysql>

其中SHOW PROFILE 的用法官网可以查询，官网PROFILE教程详解：

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
}

通过这些查询我们可以确定SQL执行的效率也为更好的优化打下基础