November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
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特殊的索引和集合类型
｜
127
因此必须指定索引或者文档使用的语言。
text
索引允许指定
"default_language"
选项，其
默认值为
"english"
，可以被设置为多种其他语言。
例如，要创建一个法语索引，可以这样做：
> db.users.createIndex({"profil" : "text",
"intérêts" : "text"},
{"default_language" : "french"})
这样一来，除非另外指定，否则这个索引会默认使用法语的词干提取机制。可以在每个文
档的基础上使用
"language"
字段来描述文档的语言，从而指定另一种词干提取语言。
> db.users.insert({"username" : "swedishChef",
... "profile" : "Bork de bork", language : "swedish"})
6.3
固定集合
MongoDB
中的“普通”集合是动态创建的，并且可以自动增长以容纳更多的数据。
MongoDB
中还有另一种集合
，名为
固定集合
，此集合需要提前创建好，而且它的大小是
固定的（参见图
6-3
）。
图 6-3：新文档被插入队列末尾
使用固定大小的集合引出了一个有趣的问题：当我们试图向一个已经满了的固定集合中插
入数据时会发生什么？答案是，固定集合的行为类似于循环队列：如果空间不足，那么最
旧的文档将被删除，新的文档将取而代之（参见图
6-4
）
。这意味着在插入新文档时，固定
集合会自动淘汰最旧的文档。
128
｜
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.