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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深入
MongoDB
｜
385
可遍历性
在某些情况下，
BSON
会牺牲空间效率
，使格式更容易被遍历。例如，字符串值会以长
度作为前缀，而不是依赖于结束符来表示字符串的结束。当
MongoDB
服务器需要对文
档进行内省（
introspect
）时，这种可遍历性非常有用。
高性能
最后，
BSON
的设
计可以快速地进行编码和解码。它使用
C
语言风格的类型表示，这
在大多数编程语言中可以十分快速地运行。
B.2
线路协议
驱动程序使用了一种轻量级的
TCP/IP
线路协议（
wire protocol
）来访问
MongoDB
服务器。
可以在
MongoDB
文档的网站中查看该协议
，但它基本上就是围绕
BSON
数据的简单封
装。例如，一个插入消息是由
20
字节的头数据
（其中包括通知服务器执行插入的代码和
消息的长度）、要插入的集合名称以及要插入的
BSON
文档列表组成的。
B.3
数据文件
在
MongoDB
的数据目录（默认为
/data/db/
）中，每个集合和每个索引都被存储为单独的
文件，其文件名与集合或索引的名称并不对应，但是可以使用
mongo shell
中的
stats
命令
来找出特定集合的相关文件。
"wiredTiger.uri"
字段包含了在
MongoDB
数据目录中对应
文件的名称。
在
sample_mflix
数据库中对
movies
集合使用
stats
命令，可以在
"wiredTiger.uri"
字段中
找到结果“
collection-14--2146526997547809066
”：
>db.movies.stats()
{
"ns" : "sample_mflix.movies", ...
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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.