Question

我有一个计数计算查询，我在我的Rails应用程序中运行了数千次，一次为数据库中的每个客户运行。

当我在MySQL客户端中运行查询并禁用查询缓存时，查询的持续时间不超过1毫秒。

然而，当我从启用了查询输出的Rails控制台运行我的任务时，我注意到在前几次查询很快之后，其余查询的时间突然从不到1毫秒突然增加到大约180毫秒

我已经减少了innodb_buffer_pool_size，以便查看行为的变化，但没有发现任何事情。

以下是控制台的输出：

  EmailCampaignReport::Open Columns (143.2ms)   SHOW FIELDS FROM `email_campaign_report_opens`
  SQL (0.3ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332330) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 333333) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332661) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332326) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332665) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 336027) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 333001) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 331983) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332668) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332316) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332325) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 331995) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 334007) 
  SQL (0.2ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 333326) 
  SQL (0.1ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332998) 
  SQL (183.9ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 334673) 
  SQL (183.7ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 336751) 
  SQL (183.6ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 333334) 
  SQL (186.3ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332663) 
  SQL (183.7ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332328) 
  SQL (186.3ms)   SELECT count(*) AS count_all FROM `email_campaign_report_opens` WHERE (customer_id = 332659)

该表中的customer_id列有一个索引。

有没有人对为什么会这样做有任何建议？

由于

Answer 1

为什么不运行一个查询？

SELECT customer_id, count(*) AS count_all FROM `email_campaign_report_opens` GROUP BY customer_id;

如果您有这么多记录，您担心将它们全部归还，那么请分批进行，但我只是不明白为什么您真的想要为每个客户运行此查询。

Answer 2

这种情况是否也会发生在您的rails应用中，或者只是在控制台中运行时才会发生这种情况？另外，您使用的是Aptana等客户端，还是在shell中运行它？

Answer 3

这是什么版本的Rails？根据您的版本和您的Ruby / Rails代码，您可能会在不使用它的情况下缓存大量数据，并且在获取新数据之前必须进行垃圾收集，这可以解释延迟。请注意，这是猜测。

Answer 4

向关联添加counter cache是不是有意义（阅读：向email_campaign_report_opens_count模型添加Customer）？当然，您必须在迁移期间初始化计数器，但它应该非常快，您甚至不需要在遍历customers表时触摸关联的表。

Rails MySQL查询时间混乱

4 个答案: