MongoDB'count（）'非常慢。我们如何改进/解决它？ [英] MongoDB 'count()' is very slow. How do we refine/work around with it?

问题描述

我目前正在使用MongoDB数百万的数据记录。我发现了一件很讨厌的事情。

当我使用count（）函数和少量查询数据集合时，它非常快。但是，当查询的数据集合包含千或甚至数百万的数据记录时，整个系统变得非常慢。

我确保我已索引所需的字段。 / p>

有人遇到过同样的事吗？

解决方案

现在有另一个优化比创建适当的索引。

  db.users.ensureIndex（{name：1}）; 
 db.users.find（{name：Andrei}）。count（）; 
  

如果你需要一些计数器，我建议尽可能的预先计算它们。使用原子性 $ inc 操作，而不使用 count（{} ）

但是mongodb们在mongodb上努力工作，所以， count（{}）根据jira 错误，在mongodb 2.1中规划的改进。

I am currently using MongoDB with millions of data records. I discovered one thing that's pretty annoying.

When I use 'count()' function with a small number of queried data collection, it's very fast. However, when the queried data collection contains thousand or even millions of data records, the entire system becomes very slow.

I made sure that I have indexed the required fields.

Has anybody encountered an identical thing? How do you do to improve that?

解决方案

There is now another optimization than create proper index.

db.users.ensureIndex({name:1});
db.users.find({name:"Andrei"}).count();

If you need some counters i suggest to precalculate them whenever it possible. By using atomic $inc operation and not use count({}) at all.

But mongodb guys working hard on mongodb, so, count({}) improvements they are planning in mongodb 2.1 according to jira bug.

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