原版书 <<50 Tips and Tricks for MongoDB Developers>> 地址:http://oreilly.com/catalog/0636920019893
皮皮书屋下载地址:http://www.ppurl.com/2011/05/50-tips-and-tricks-for-mongodb-developers.html
本书的所有翻译地址:http://blog.csdn.net/crazyjixiang/article/category/858638
翻译目的:MongoDB资料国内很少,书就更不必说了,借助对MongoDB的理解为大家做点贡献,如果有翻译有误的地方请指正,不能误入子弟,谢谢!
译者: Crazybaby
对Tip# 26 翻译如下:
保持你的数据组织是分层的 ,不仅仅是组织化的,而且MongoDB可以在没有索引的情况下搜索上更快(在某些情况下)。
比如,设想你要在没有索引的情况下查询一些数据集。根据之前提及的,MongoDB不得不从头到尾在每个集合每个文档中进行标准匹配,根据你的文档结构,这将花费不同的时间。
让我们看下user集合的平面结构:
现在,我们来试着查询:
> db.users.find({"zip" : "10003"})
MongoDB内部会怎么样查询?它不得不从头到尾每个集合中的单元中查询zip单元,如图所示:
现在,通过内嵌集合,我们可以创建我们自己的"tree" 让MongoDB查询更快些.试想我们把结构改成这样:
现在我们来试着这样查询:
> db.users.find({"address.zip" : "10003"})
MongoDB在找到address必要的前缀之前,不得不查询_id,name和online,然后再查找zip这个单元。使用一个合理的分层结构使MongoDB不不需要对每个单元进行匹配。
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