mongo之$rename更新一个字段的名称（可批量）

$rename操作逻辑执行$unset 老名称和新的名称，然后执行 $set新名称运行。因此，操作可能不保留文档中字段的顺序; 即重命名的字段可以在文档内移动。

1、重命名字段：一级字段

格式：

db.students.updateMany( {}, { $rename: { "nmae": "name" } } )

eg：

#原集合
{
  "_id": 1,
  "alias": [ "The American Cincinnatus", "The American Fabius" ],
  "mobile": "555-555-5555",
  "nmae": { "first" : "george", "last" : "washington" }
}

{
  "_id": 2,
  "alias": [ "My dearest friend" ],
  "mobile": "222-222-2222",
  "nmae": { "first" : "abigail", "last" : "adams" }
}

{
  "_id": 3,
  "alias": [ "Amazing grace" ],
  "mobile": "111-111-1111",
  "nmae": { "first" : "grace", "last" : "hopper" }
}

#修改：批量把所有的nmae 字段改成name,也可以在第一个花括号里面指定修改哪一个id记录的nmae
db.students.updateMany( {}, { $rename: { "nmae": "name" } } )

#输出：
{
  "_id": 1,
  "alias": [ "The American Cincinnatus", "The American Fabius" ],
  "mobile": "555-555-5555",
  "name": { "first" : "george", "last" : "washington" }
}

{
   "_id" : 2,
   "alias" : [ "My dearest friend" ],
   "mobile" : "222-222-2222",
   "name" : { "first" : "abigail", "last" : "adams" }
}

{ "_id" : 3,
  "alias" : [ "Amazing grace" ],
  "mobile" : "111-111-1111",
  "name" : { "first" : "grace", "last" : "hopper" } }

2、重命名嵌入文档中的字段

eg：

#元集合：
{
  "_id": 1,
  "alias": [ "The American Cincinnatus", "The American Fabius" ],
  "mobile": "555-555-5555",
  "name": { "first" : "george", "last" : "washington" }
}

{
   "_id" : 2,
   "alias" : [ "My dearest friend" ],
   "mobile" : "222-222-2222",
   "name" : { "first" : "abigail", "last" : "adams" }
}

{ "_id" : 3,
  "alias" : [ "Amazing grace" ],
  "mobile" : "111-111-1111",
  "name" : { "first" : "grace", "last" : "hopper" } }
#修改
db.students.update( { _id: 1 }, { $rename: { "name.first": "name.fname" } } )
#结果

{
  "_id" : 1,
  "alias" : [ "The American Cincinnatus", "The American Fabius" ],
  "mobile" : "555-555-5555",
  "name" : { "fname" : "george", "last" : "washington" }
}

注释：

×重命名不存在的字段
重命名字段并且现有字段名称引用不存在的字段时，$rename操作员不执行任何操作