简化MongoDB中的graphLookup输出

Question

我有一个集合"people"格式为:

{ "_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(比如Kid)的祖先，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"  
}  
}  
])

返回

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

我卡住的地方是如何将这个输出数据重构成一个单层数组，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)。

任何帮助都将非常感激!

Answer 1

• 只需将startWith从parentID更改为_id，这将返回ancestors与当前文档
• $project显示必填字段

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

访问数组:

finalResult = result[0]['ancestors']