MongoDB中的collections就是一系列 BSON documents的集合，相当于关系数据库中的表。
collection将会在第一次往里面插入documents时创建
> show dbs;
admin (empty)
foo 0.0625GB
fucker 0.0625GB
local (empty)
test 0.0625GB
> use fucker;
switched to db fucker
> show collections;
fucker
system.indexes
users
> db.test.insert({ "id" : 1 });
> show collections;
fucker
system.indexes
test
users
collection名最大长度为128个字符，建议不要超80/90个字符
可以使用如下命令来创建collection（一般用于创建Capped collections）
> show collections;
fucker
system.indexes
test
users
> //mongo shell
> db.createCollection("mycoll",{capped:true, size:100000}) //size is in bytes
{ "ok" : 1 }
> show collections;
fucker
mycoll
system.indexes
test
users
> show collections;
fucker
mycoll
system.indexes
test
users
> db.runCommand( {create:"mycoll_1", capped:true, size:100000} )
{ "ok" : 1 }
> show collections;
fucker
mycoll
mycoll_1
system.indexes
test
users
> show collections;
fucker
mycoll
mycoll_1
system.indexes
test
users
> db.mycoll.renameCollection("Yourcoll");
{ "ok" : 1 }
> show collections;
Yourcoll
fucker
mycoll_1
system.indexes
test
users
> show collections;
Yourcoll
fucker
mycoll_1
system.indexes
test
users
> use admin;
switched to db admin
> db.runCommand( { renameCollection: "fucker.Yourcoll", to: "fucker.Hiscoll"} );
{ "ok" : 1 }
> use fucker;
switched to db fucker
> show collections;
Hiscoll
fucker
mycoll_1
system.indexes
test
users