在graphLookup中简化MongoDB输出

Question

我有一个收集“人物”的形式：

{ "_id" : 1, "name" : "Grandma"}   
{ "_id" : 2, "name" : "Mum", "parentID": "1"}  
{ "_id" : 3, "name" : "Uncle", "parentID": "1"}  
{ "_id" : 4, "name" : "Kid", "parentID": "2"}  
{ "_id" : 5, "name" : "Sister", "parentID": "2"}

要获得某个人的祖先(比如Kid)，我可以使用简单的match和graphLookup，如下所示：

people.aggregate([  
    {$match: {_id: "3"}},  
    {$graphLookup:  
        {  
        from: "people",  
        startWith: "$parentID",  
        connectFromField: "parentID",  
        connectToField: "_id",  
        as: "ancestors"  
        }  
    }  
])

会回来的

{ "_id" : 3, "name" : "Kid", "parentID": "2", "ancestors": [
    { "_id" : 1, "name" : "Grandma"},
    { "_id" : 2, "name" : "Mum", "parentID": "1"}]
}

我被困住的地方是如何将输出数据重构为一个单层数组，这样：

array = [  
{ "_id" : 1, "name" : "Grandma"},    
{ "_id" : 2, "name" : "Mum", "parentID": "1"},  
{ "_id" : 3, "name" : "Kid", "parentID": "2"}  
]

(数组顺序不重要)。

任何帮助都将不胜感激！

Answer 1

• 只需将startWith从parentID更改为_id，这将返回带有当前文档的ancestors
• 显示所需字段的$project

result = people.aggregate([
  { $match: { _id: "3" } },
  {
    $graphLookup: {
      from: "collection",
      startWith: "$_id",
      connectFromField: "parentID",
      connectToField: "_id",
      as: "ancestors"
    }
  },
  {
    $project: {
      _id: 0,
      ancestors: 1
    }
  }
])

游乐场

通过以下方式访问数组：

finalResult = result[0]['ancestors']