如何將陣列轉換為mongodb/mongoose聚合中的物件？

共有三個集合。

離開

• _ID
• 用戶（參考用戶模型）
• 地位

離開批準

• _ID
• 離開（參考離開模型）
• auditUser（參考用戶模型）
• 角色

用戶

• _ID
• 姓名

對離開集合執行查找階段后：

Leave.aggregate([
    $lookup: {
        from: 'leaveapprovals',
        localField: '_id',
        foreignField: 'leave',
        as: 'approverRecommender'
    }
])

{
    _id: ObjectId('6262851ab059b81fd9076532'),
    user: ObjectId('21ca9490192add08fa385aec'),
    status: "pending",
    approverRecommender: [
        {
            _id: ObjectId('6262851ab059b81fd907653d'),
            leave: ObjectId('6262851ab059b81fd9076532'),
            auditUser: ObjectId('61ca9490192add08fa385aeb'),
            role: "recommender"    
        },
        {
            _id: ObjectId('6262851ab059b81fd907653d'),
            leave: ObjectId('6262851ab059b81fd9076532'),
            auditUser: ObjectId('71ca9490192add08fa385aec'),
            role: "approver"    
        }
    ]
}

我想要得到的結果是：

{
    _id: ObjectId('6262851ab059b81fd9076532'),
    user: ObjectId('21ca9490192add08fa385aec'),
    status: "pending",
    recommender: {
        _id: ObjectId('61ca9490192add08fa385aeb'),
        name: "Andrew"
    },
    approver: {
        _id: ObjectId('71ca9490192add08fa385aec'),
        name: "James"
    }
}

我怎樣才能改變它？

uj5u.com熱心網友回復：

1. $lookup- 需要一個嵌套的$lookup. 首先$lookup用管道加入leave和leaveapprovals收集。而內部 $lookup加入user集合和回傳auditUser和role欄位。

2. $set-

   2.1。對于approver欄位，過濾角色approverRecommender的陣列欄位approver并通過$first.

   2.2. 對于recommender欄位，過濾角色approverRecommender的陣列欄位recommender并通過$first.

3. $project- 裝飾輸出檔案。用于$first回傳第一個檔案，approver并且recommender從結果 2 開始，兩個欄位都回傳為陣列。

db.leave.aggregate([
  {
    $lookup: {
      from: "leaveapprovals",
      let: {
        leaveId: "$_id"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $eq: [
                "$$leaveId",
                "$leave"
              ]
            }
          }
        },
        {
          $lookup: {
            from: "user",
            localField: "auditUser",
            foreignField: "_id",
            as: "auditUser"
          }
        },
        {
          $project: {
            auditUser: 1,
            role: 1
          }
        }
      ],
      as: "approverRecommender"
    }
  },
  {
    "$set": {
      approver: {
        "$first": {
          "$filter": {
            "input": "$approverRecommender",
            "cond": {
              $eq: [
                "$$this.role",
                "approver"
              ]
            }
          }
        }
      },
      recommender: {
        "$first": {
          "$filter": {
            "input": "$approverRecommender",
            "cond": {
              $eq: [
                "$$this.role",
                "recommender"
              ]
            }
          }
        }
      }
    }
  },
  {
    "$set": {
      approver: {
        "$first": {
          "$filter": {
            "input": "$approverRecommender",
            "cond": {
              $eq: [
                "$$this.role",
                "approver"
              ]
            }
          }
        }
      },
      recommender: {
        "$first": {
          "$filter": {
            "input": "$approverRecommender",
            "cond": {
              $eq: [
                "$$this.role",
                "recommender"
              ]
            }
          }
        }
      }
    }
  },
  {
    $project: {
      _id: 1,
      user: 1,
      status: 1,
      "approver": {
        $first: "$approver.auditUser"
      },
      "recommender": {
        $first: "$recommender.auditUser"
      }
    }
  }
])

示例 Mongo Playground

標籤：mongodb 猫鼬 聚合框架

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