在MongoDb中，如何應用文檔中存在的排序內部字段？

Question

我的文件看起來像這樣

{ 
    field1: somevalue, 
    name:xtz 


    nested_documents: [ // array of nested document 
    { x:"1", y:"2" }, // first nested document 
    { x:"2", y:"3" }, // second nested document 
    { x:"-1", y:"3" }, // second nested document 
    // ...many more nested documents 
    ] 
} 

如何可以存在於nested_documents對數據進行排序？
預期的答案如下：

nested_documents: [ { x:"-1", y:"3" },{ x:"1", y:"2" },{ x:"2", y:"3" }] 

Answer 1

要做到這一點，你將不得不使用聚合框架

db.test.aggregate（[{$開卷： '$ nested_documents'}，{ $排序：{ 'nested_documents.x'： 1}}]）

此返回

"result" : [ 
    { 
      "_id" : ObjectId("5139ba3dcd4e11c83f4cea12"), 
      "field1" : "somevalue", 
      "name" : "xtz", 
      "nested_documents" : { 
        "x" : "-1", 
        "y" : "3" 
      } 
    }, 
    { 
      "_id" : ObjectId("5139ba3dcd4e11c83f4cea12"), 
      "field1" : "somevalue", 
      "name" : "xtz", 
      "nested_documents" : { 
        "x" : "1", 
        "y" : "2" 
      } 
    }, 
    { 
      "_id" : ObjectId("5139ba3dcd4e11c83f4cea12"), 
      "field1" : "somevalue", 
      "name" : "xtz", 
      "nested_documents" : { 
        "x" : "2", 
        "y" : "3" 
      } 
    } 
], 
"ok" : 1 

希望這會有所幫助