MongoDB创建集合命令db.createCollection详解
MongoDB创建集合命令db.createCollection详解
完整的命令如下：
db.createCollection(name, {capped:
name:集合的名字
capped:是否启用集合限制，如果开启需要制定一个限制条件，默认为不启用，这个参数没有实际意义
size:限制集合使用空间的大小，默认为没有限制
max:集合中最大条数限制，默认为没有限制
autoIndexId:是否使用_id作为索引，默认为使用(true或false)
size的优先级比max要高
常用方法介绍：
1、一般来说，我们创建集合用db.createCollection(name),如：db.createCollection("log"),创建一个名字为log的集合，没有任何的大小，数量限制，使用_id作为默认索引；
2、限制集合空间的大小：db.createCollection("log",{size:1024})或db.createCollection("log",{capped:true,size:1024}),创建一个名字为log集合，限制它的空间大小为1M，如果超过1M的大小，则会删除最早的记录；
3、限制集合的最大条数：db.createCollection("log",{max:1024})，创建一个名字为log集合，最大条数为1024条，超过1024再插入数据的话会删除最早的一条记录。这个不能使用capped:true，否则会报错；
4、即限制最大条数有限制使用空间大小：db.createCollection("log",{size:1024,max:1024})或db.createCollection("log",{capped:true,size:1024,max:1024})，，限制集合最大使用空间为1M，最大条数为1024条
以上是参考官方文档和实际测试得出的，也可以看出capped参数没有什么用处，用不用都可以。
MongoDB 的详细介绍：请点这里
MongoDB 的下载地址：请点这里
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