Mongo Aggregation Pipeline $查找嵌套嵌入文檔和$ project

Question

我有兩個集合users和`groups。讓我們假裝當前收藏中有以下數據。

的users收集具有以下文件

{ 
    "_id":"57a944390b1acf0d069388c1", 
    "first":"John", 
    "last":"Smith", 
    "email":"John.Smith@gmail.com", 
    "groups":[ 
     { 
     "id":"57aab09c0b1acf135a6b6856", 
     "name":"Group A" 
     }, 
     { 
     "id":"57aab0ed0b1acf135a6b6857", 
     "name":"Group B" 
     }, 
     { 
     "id":"57b008be31a5a202ee4ff47b", 
     "name":"Group C" 
     } 
    ] 
} 

的groups收集有以下兩個文件

[ 
    { 
     "_id":"57aab0ed0b1acf135a6b6857", 
     "name":"Group B", 
     "requests":[ 
     { 
      "_id":"57b14b1831a5a2756fbc9873", 
      "description":"Request A", 
      "denied_requests":[ ] 
     } 
     ] 
    } { 
     "_id":"57b008be31a5a202ee4ff47b", 
     "name":"Group C", 
     "requests":[ 
     { 
      "_id":"57b14c2131a5a2756fbc9874", 
      "description":"Request B", 
      "denied_requests":[ ] 
     }, 
     { 
      "_id":"57b14e3131a5a2756fbc9875", 
      "description":"Request C", 
      "denied_requests":[ 
       "57a944390b1acf0d069388c1" 
      ] 
     } 
     ] 
    } 
] 

我需要做的是使用聚合管道來查詢用戶的所有請求排除用戶拒絕的請求。

我想這將包括以下psudo步驟user_id作爲問題的輸入。

• $match用戶_id字段
• $project的組使用先前步驟
• $lookup的結果id S上的id從$project上users.groups在groups集合的_id
• $match在requests上，根據請求，沒有當前用戶標識denied_requests數組。

表示用戶_id採樣輸入

樣例輸入到這將是57a944390b1acf0d069388c1

樣本輸出

樣本輸出到這將是要求將下列表用戶沒有拒絕。

[ 
     { 
      "_id":"57b14b1831a5a2756fbc9873", 
      "description":"Request A", 
      "denied_requests":[] 
     }, 
     { 
      "_id":"57b14c2131a5a2756fbc9874", 
      "description":"Request B", 
      "denied_requests":[ ] 
     } 
] 

Answer 1

運行下面的管道，它應該給你想要的結果：

var userId = "57a944390b1acf0d069388c1"; 
db.users.aggregate([ 
    { "$match": { "_id": userId } }, 
    { "$unwind": "$groups" }, 
    { 
     "$lookup": { 
      "from": "groups", 
      "localField": "groups.id", 
      "foreignField": "_id", 
      "as": "group" 
     } 
    }, 
    { "$unwind": "$group" }, 
    { 
     "$project": { 
      "requests": { 
       "$filter": { 
        "input": "$group.requests", 
        "as": "item", 
        "cond": { "$not": { 
         "$setIsSubset": [ 
          [userId], "$$item.denied_requests" 
         ] 
        } } 
       } 
      } 
     } 
    }, 
    { "$unwind": "$requests" }, 
    { 
     "$project": { 
      "_id": "$requests._id", 
      "description": "$requests.description", 
      "denied_requests": "$requests.denied_requests" 
     } 
    } 
])