解析Mysql Profiling的使用

2024-07-24 12:48:24

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profiling是个很好用的mysql性能分析工具，今儿就来试验下profiling的功能。感谢有爱玫瑰的博文：
mysql 的 sql 性能分析器主要用途是显示 sql 执行的整个过程中各项资源的使用情况。分析器可以更好的展示出不良 SQL 的性能问题所在。
下面我们举例介绍一下MySQL SQL Profiler的使用方法：
首先，开启 MySQL SQL Profiler
复制代码代码如下:

mysql> SELECT @@profiling;
    +-------------+
    | @@profiling |
    +-------------+
    | 0 |
    +-------------+
    1 row in set (0.00 sec)
    mysql> SET profiling = 1;
    Query OK, 0 rows affected (0.00 sec)
    mysql> SELECT @@profiling;
    +-------------+
    | @@profiling |
    +-------------+
    | 1 |
    +-------------+

1 row in set (0.00 sec)默认情况下 profiling 的值为 0 表示 MySQL SQL Profiler 处于 OFF 状态，开启 SQL 性能分析器后 profiling 的值为 1.
通过 sql 性能分析器，我们来对比一下下列语句前后 2 次执行过程的差异，对我们了解 sql 的详细执行过程是非常有帮助的。
复制代码代码如下:

mysql> create table t_engines select * from t_engines1;
    Query OK, 57344 rows affected (0.10 sec)
    Records: 57344 Duplicates: 0 Warnings: 0
    mysql> select count(*) from t_engines;
    +----------+
    | count(*) |
    +----------+
    | 57344 |
    +----------+
    1 row in set (0.00 sec)
    mysql> select count(*) from t_engines;
    +----------+
    | count(*) |
    +----------+
    | 57344 |
    +----------+
    1 row in set (0.00 sec)
    mysql> SHOW PROFILES;
    +----------+------------+-------------------------------------------------+
    | Query_ID | Duration | Query |
    +----------+------------+-------------------------------------------------+
    | 26 | 0.10213775 | create table t_engines select * from t_engines1 |
    | 27 | 0.00032775 | select count(*) from t_engines |
    | 28 | 0.00003850 | select count(*) from t_engines |
    +----------+------------+-------------------------------------------------+
    15 rows in set (0.01 sec)
    mysql> SHOW PROFILE FOR QUERY 27;
    +--------------------------------+------------+
    | Status | Duration |
    +--------------------------------+------------+
    | (initialization) | 0.00000425 |
    | checking query cache for query | 0.00004050 |
    | checking permissions | 0.00001050 |
    | Opening tables | 0.00018250 |
    | System lock | 0.00000450 |
    | Table lock | 0.00001775 |
    | init | 0.00001075 |
    | optimizing | 0.00000550 |
    | executing | 0.00002775 |
    | end | 0.00000450 |
    | query end | 0.00000325 |
    | storing result in query cache | 0.00000400 |
    | freeing items | 0.00000400 |
    | closing tables | 0.00000500 |
    | logging slow query | 0.00000300 |
    +--------------------------------+------------+
    15 rows in set (0.00 sec)
    mysql> SHOW PROFILE FOR QUERY 28;
    +-------------------------------------+------------+
    | Status | Duration |
    +-------------------------------------+------------+
    | (initialization) | 0.00000350 |
    | checking query cache for query | 0.00000750 |
    | checking privileges on cached query | 0.00000500 |
    | checking permissions | 0.00000525 |
    | sending cached result to client | 0.00001275 |
    | logging slow query | 0.00000450 |
    +-------------------------------------+------------+
    6 rows in set (0.00 sec) mysql> SELECT sum( FORMAT(DURATION, 6)) AS DURATION FROM INFORMATION_SCHEMA.PROFILING WHERE QUERY_ID =27 ORDER BY SEQ;
    +----------+
    | DURATION |
    +----------+
    | 0.000326 |
    +----------+
    1 row in set (0.00 sec) mysql> SELECT sum( FORMAT(DURATION, 6)) AS DURATION FROM INFORMATION_SCHEMA.PROFILING WHERE QUERY_ID =28 ORDER BY SEQ;
    +----------+
    | DURATION |
    +----------+
    | 0.000039 |
    +----------+
    1 row in set (0.00 sec)

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