Mysql查询中的性能滞后答案

【问题标题】：Performace Lag in Mysql queryMysql查询中的性能滞后
【发布时间】：2012-08-31 13:37:24
【问题描述】：

这个mysql查询需要5分20秒来执行

SELECT PROVIDER, COUNT(DISTINCT(NAME)) FROM   Test  WHERE NAME NOT IN (SELECT NAME 
FROM Test   WHERE OPERATION = 'SIGN_IN' and Test.CREATED_TIME BETWEEN UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) *    1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000) 
AND Test.CREATED_TIME BETWEEN UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) * 1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000 AND OPERATION='VALIDATE'  GROUP BY PROVIDER;

解释给出以下结果

explain SELECT  PROVIDER, COUNT(DISTINCT(NAME)) FROM   Test  WHERE NAME NOT IN  
(SELECT NAME  FROM Test   WHERE OPERATION = 'SIGN_IN' and Test.CREATED_TIME BETWEEN 
UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) * 1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000) AND         Test.CREATED_TIME    BETWEEN UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) * 1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000 AND OPERATION='VALIDATE'  GROUP BY PROVIDER;
+----+--------------------+-----------------+----------------+----------------------------------------------------------------------+-------------------------+---------+------+--------+------------------------------------+
| id | select_type        | table           | type           | possible_keys                                                        | key                     | key_len | ref  | rows   | Extra                              |
+----+--------------------+-----------------+----------------+----------------------------------------------------------------------+-------------------------+---------+------+--------+------------------------------------+
|  1 | PRIMARY            | Test | ALL            | Test_CTndx,Test_CORndx                         | NULL                    | NULL    | NULL | 137523 | Using where; Using filesort        |
|  2 | DEPENDENT SUBQUERY | Test | index_subquery | Test_NAMEndx,Test_CTndx,Test_CORndx | Test_NAMEndx | 303     | func |    148 | Using where; Full scan on NULL key |
+----+--------------------+-----------------+----------------+----------------------------------------------------------------------+-------------------------+---------+------+--------+------------------------------------+

表中的行数为 50,000。

我该如何优化呢？

【问题讨论】：

标签： mysql performance explain

【解决方案1】：

重写查询以将 NOT IN 替换为等效的 NOT EXISTS 语句应该更快。

例如，尝试这样的事情：

SELECT t1.PROVIDER, COUNT(DISTINCT(t1.NAME)) 
FROM   Test t1 
WHERE t1.CREATED_TIME BETWEEN UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) * 1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000 
AND t1.OPERATION='VALIDATE'  
and NOT EXISTS (
  select null
  from test t2
  where t2.OPERATION = 'SIGN_IN' 
  and t2.CREATED_TIME BETWEEN UNIX_TIMESTAMP(CURRENT_DATE()  - INTERVAL 1 DAY) *    1000  AND UNIX_TIMESTAMP(CURRENT_DATE()) * 1000
  and t2.name = t1.name
)
GROUP BY t1.PROVIDER;

【讨论】：