$rename¶

Definition定义¶

$rename¶

The $rename operator updates the name of a field and has the following form:$rename运算符更新字段的名称，其形式如下：

{$rename: { <field1>: <newName1>, <field2>: <newName2>, ... } }

The new field name must differ from the existing field name. 新字段名必须与现有字段名不同。To specify a <field> in an embedded document, use dot notation.要在嵌入式文档中指定<field>，请使用点表示法。

Consider the following example:考虑下面的例子：

db.students.update( { _id: 1 }, { $rename: { 'nickname': 'alias', 'cell': 'mobile' } } )

This operation renames the field nickname to alias, and the field cell to mobile.此操作将字段nickname重命名为alias，将字段cell重命名为mobile。

Behavior行为¶

The $rename operator logically performs an $unset of both the old name and the new name, and then performs a $set operation with the new name. $rename运算符在逻辑上对旧名称和新名称执行$unset，然后对新名称执行$set操作。As such, the operation may not preserve the order of the fields in the document; i.e. the renamed field may move within the document.因此，该操作可能不会保留文档中字段的顺序；亦即，重命名的字段可能会在文档中移动。

If the document already has a field with the <newName>, the $rename operator removes that field and renames the specified <field> to <newName>.如果文档已经有一个带有<newName>的字段，$rename运算符将删除该字段，并将指定的<field>重命名为<newName>。

If the field to rename does not exist in a document, $rename does nothing (i.e. no operation).如果要重命名的字段在文档中不存在，$rename不执行任何操作（即不执行任何操作）。

For fields in embedded documents, the $rename operator can rename these fields as well as move the fields in and out of embedded documents. 对于嵌入文档中的字段，$rename运算符可以重命名这些字段，并将字段移入和移出嵌入文档。$rename does not work if these fields are in array elements.如果这些字段位于数组元素中，$rename不起作用。

Examples示例¶

A collection students contains the following documents where a field nmae appears misspelled, i.e. should be name:students集合包含以下文档，其中字段nmae出现拼写错误，即应为name：

{
  "_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" }
}

The examples in this section successively updates the documents in the collection.本节中的示例依次更新了集合中的文档。

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

{
  "_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" } }

db.students.update( { _id: 1 }, { $rename: { "name.first": "name.fname" } } )

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

db.students.update( { _id: 1 }, { $rename: { 'wife': 'spouse' } } )