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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256
｜
第
15
章
在
MongoDB 3.6
之前，可以创建一个独立的
mongod
进程作为一个分片。这在
MongoDB 3.6
之后的版本中不再可行。所有分片都必须是副本集。
15.2.4
增加集群容量
如果需要更多的容量，则可以添加更多的分片。要添加新的空分片，可以先创建一个副
本集。确保副本集与任何其他分片具有不同的名称。初始化并拥有一个主节点后，通过
mongos
运行
addShard
命令将其添加到集群中，并指定新副本集的名称及其主机名作为种子。
如果有几个现有的副本集不是分片，那么只要没有任何同名的数据库，就可以将它们全部
作为新分片添加到集群中。如果有一个带有
blog
数据库的副本集
，一个带有
calendar
数据
库的副本集，以及一个带有
mail
、
tel
和
music
数据库的副本集
，那么可以将每个副本集作
为一个分片添加到集群中，最终得到一个拥有
3
个分片和
5
个数据库的集群
。不过，如果
还有第四个副本集，它也有一个名为
tel
的数据库，那么
mongos
将拒绝将其添加到集群中。
15.2.5
数据分片
只有在明确指定了规则之后，
MongoDB
才会自动对数据进行拆分。在希望对数据进行拆
分时，必须明确地告知数据库和集合。假设你有一个
music
数据
库，现在希望在
"name"
键
上对
artists
集合进行分片。首先，为数据库启用分片：
> sh.enableSharding("music")
对数据库分片是对其中集合进行分片的先决条件。
在数据库级别上启用了分片后，就可以运行
sh.shardCollection()
来对集合进行分片了： ...
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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.