如何在MongoDB中过滤聚合元素？

在官方的mongo文档中，有一个示例演示了

$graphLookup

，该示例在每个结果元素中包含

reportingHierarchy

字段。但如何过滤某些关键帧内设置的最终元素

{ "_id": 1, "name": "Dev", final: false }
{ "_id": 2, "name": "Eliot", "reportsTo" : "Dev", final: false }
{ "_id": 3, "name": "Ron", "reportsTo" : "Eliot", final: false }
{ "_id": 4, "name": "Andrew", "reportsTo" : "Eliot", final: false }
{ "_id": 5, "name": "Asya", "reportsTo" : "Ron", final: true }
{ "_id": 6, "name": "Dan", "reportsTo" : "Andrew", final: true }

我需要向这个查询添加什么，以确定我只对带有

final:true

param的记录感兴趣，但仍然获得所有

reportingHierarchy

树

db.employees.aggregate( [
   ???
   {
      $graphLookup: {
         from: "employees",
         startWith: "$reportsTo",
         connectFromField: "reportsTo",
         connectToField: "name",
         as: "reportingHierarchy"
      }
   }
] )

预期产出：

{ "_id": 5, "name": "Asya", "reportsTo" : "Ron", final: true,
    "reportingHierarchy": [
        { "_id": 1, "name": "Dev", final: false },
        { "_id": 2, "name": "Eliot", "reportsTo" : "Dev", final: false },
        { "_id": 3, "name": "Ron", "reportsTo" : "Eliot", final: false }
    ]
}
{ "_id": 6, "name": "Dan", "reportsTo" : "Andrew", final: true,
    "reportingHierarchy": [
        { "_id": 1, "name": "Dev", final: false },
        { "_id": 2, "name": "Eliot", "reportsTo" : "Dev", final: false },
        { "_id": 4, "name": "Andrew", "reportsTo" : "Eliot", final: false }
    ]
}

---

首先使用

$match

筛选出所需的记录

db.employees.aggregate([
   { 
       $match: { final: true } 
   },
   {
      $graphLookup: {
         from: "employees",
         startWith: "$reportsTo",
         connectFromField: "reportsTo",
         connectToField: "name",
         as: "reportingHierarchy"
      }
   }
])

你可以试试这个

db.employees.aggregate([{
            $match: {
                    "final": true
            }
        }, {
            $graphLookup: {
                from: "employees",
                startWith: "$reportsTo",
                connectFromField: "reportsTo",
                connectToField: "name",
                as: "reportingHierarchy"
            }
        }, {
            $addFields: {
                reportingHierarchy: {
                    $filter: {
                        input: "$reportingHierarchy",
                        as: "reportingHierarchy_field",
                        cond: {
                            $and: [{
                                    $eq: ["$$reportingHierarchy_field.final", true]
                                }
                            ]
                        }
                    }
                },
            }
        }
    ])

---

你能分享你的预期产出吗？我找到了一个选择，就是这样做。只要查询只是一个过滤器链，我们就可以过滤

$graphLookup

结果，就像这样：

{$match:{“final”：true}}

不知道它对不对，因为我们没有隔离初始集。@MuhammadFaizan，我刚刚更新了我的问题。这应该行得通。你为什么只在一个查询中使用

$和
。@MuhammadFaizan哦，是的，你是对的，这是我的错误。对此表示抱歉。