awsmysql副本滞后_托管在Amazonaws中的Mysql有时非常慢

我们有一个数据库,表包含超过200万条记录.数据库托管在Amazon aws服务器中.

有时“选择”查询执行时间非常慢.这种缓慢执行背后的原因是什么？

我的一个疑问是：

select UserDID, count(*) from exportusers

group by UserDID

having count(*) > 1;

查询说“执行查询…”,它永远不会结束.我强行退出查询浏览器.

这是我对select语句的解释

mysql> Explain select count(*) from exportusers where status != &＃39;active&＃39; and PREndDate

+----+-------------+------------+-------+-----------------------------------------------------------------------+--------------------------+---------+------+---------+------------------------------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+------------+-------+-----------------------------------------------------------------------+--------------------------+---------+------+---------+------------------------------------+

| 1 | SIMPLE | exportusers | range | index_jobs_on_DTModified,index_jobs_on_PREndDate,index_jobs_on_Status | index_jobs_on_DTModified | 5 | NULL | 2377287 | Using index condition; Using where |

+----+-------------+------------+-------+-----------------------------------------------------------------------+--------------------------+---------+------+---------+------------------------------------+

1 row in set (0.30 sec)