Rails MySQL查询时间混淆

我有一个计算计算查询，我在Rails应用程序中运行了数千次，每次在db中有一个客户。Rails MySQL查询时间混淆

当我在查询缓存禁用的MySQL客户端中运行查询时，查询最后需要1ms以上。

但是，当我从Rails控制台启动查询输出时启动我的任务后，我注意到在开始的几个查询非常快之后，时间突然从小于1ms增加到大约180ms，查询。

我减少了innodb_buffer_pool_size以查看行为的变化，但没有注意到任何东西。

下面是从控制台输出：

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)

有在该表中的CUSTOMER_ID列的索引。

有没有人有任何建议，为什么会发生这种情况？

感谢

来源

2010-01-29 johnnymire

你可以发表你的表模式，所以我们可以看到索引等？ – UltimateBrent 2010-01-30 00:03:06

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;

如果你有，你是担心回国再把它们做分批如此多的记录，但我只是不明白你为什么会真的要运行此查询为每一位顾客。

来源

2010-01-30 00:23:56

为什么我不这么想！谢啦。 – johnnymire 2010-02-01 14:29:54

很高兴为您工作。在ActiveRecord中使用对象和迭代器完成所有事情的想法很容易，但有时候一点SQL最好。 – 2010-02-01 14:45:50

这是否会发生在你的Rails应用程序一样好，甚至当你在控制台中运行它这只是发生的呢？另外，你使用的是Aptana这样的客户端，还是你在shell中运行它？

来源

2010-01-29 16:47:23 corprew

这是在shell中运行的，它确实也发生在Rails应用程序中。 – johnnymire 2010-01-29 23:27:46

这是什么版本的Rails？根据您的版本和您的Ruby/Rails代码，您可能会缓存大量数据而不使用它，过了一段时间后，必须在获取新数据之前进行垃圾回收，这可能会解释延迟。这是一个猜测，介意你。

来源

2010-01-29 18:36:16 Trevoke

它的导轨版本2.3.2 – johnnymire 2010-01-29 23:26:22

将counter cache添加到关联中是否有意义（请参阅：将email_campaign_report_opens_count添加到您的Customer模型中）？当然，你必须在迁移过程中初始化计数器，但它应该非常快，甚至不需要在走客户表时触摸相关的表格。

来源

2010-01-29 22:39:12 hurikhan77

好的建议。这几乎是我正在做的事情，我在客户模型中有一个类似的计数字段，该字符正在通过这个脚本进行更新以获得所有的计数。在创建关联时更新计数器缓存可能会更好。在初始迁移过程中仍然会遇到查询速度问题，但至少这是一次性迁移。 – johnnymire 2010-01-29 23:43:07

Rails MySQL查询时间混淆

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