檢查當前實體的id是否在具有Mongoose聚合的子陣列內

db.Product.aggregate([
  {
    $match: {
      $or: [
        {
          "message": {
            $regex: "he"
          }
        },
        {
          "field3": {
            $regex: "s"
          }
        }
      ]
    }
  },
  {
    $lookup: {
      from: "User",
      localField: "_id",
      foreignField: "favorite",
      as: "join"
    }
  },
  {
    $addFields: {
      favorited: {
        $cond: [
          {
            $in: [
              "$_id",
              "$join.favorite"
            ]
          },
          true,
          false
        ]
      }
    }
  }
])

我很困惑為什么這不起作用。它應該回傳 true，但我沒有得到預期的結果。我可以使它與 $function 一起作業，但我不能使用 $function，因為我使用的 MongoDB 版本是 4.2 而不是 $function 所需的 4.4。

[
  {
    "_id": "60508eeb52a2ab598a013bb9",
    "favorited": false,
    "field1": false,
    "field2": 1,
    "field3": "something",
    "join": [],
    "message": "hello"
  },
  {
    "_id": "60508f4152a2ab598a013bbb",
    "favorited": true,
    "field1": false,
    "field2": 1,
    "field3": "s1",
    "join": [
      {
        "_id": ObjectId("60508f4152a2ab598a013bbb"),
        "aId": ObjectId("60508f2852a2ab598a013bba"),
        "favorite": [
          "60508f4152a2ab598a013bbb",
          "60508f4552a2ab598a013bbc"
        ]
      },
      {
        "_id": ObjectId("60508f4552a2ab598a013bbc"),
        "aId": ObjectId("60508f2852a2ab598a013bba"),
        "favorite": [
          "60508f4152a2ab598a013bbb",
          "60508f4552a2ab598a013bbc"
        ]
      },
      {
        "_id": ObjectId("605090a452a2ab598a013bbd"),
        "aId": ObjectId("60508eeb52a2ab598a013bb9"),
        "favorite": [
          "60508f4152a2ab598a013bbb",
          "60508f4552a2ab598a013bbc"
        ]
      }
    ],
    "message": "hello"
  },
  {
    "_id": "60508f2852a2ab665a013bba",
    "favorited": false,
    "field1": false,
    "field2": 1,
    "field3": "s1",
    "join": [],
    "message": "hello"
  }
]

我期待上述結果。

https://mongoplayground.net/p/kM80POZ8rSq

運算式可以包括欄位路徑、文字、系統變數、運算式物件和運算式運算子。運算式可以嵌套。

https://www.mongodb.com/docs/manual/meta/aggregation-quick-reference/#std-label-aggregation-expressions

uj5u.com熱心網友回復：

如果您嘗試讀取favoritein的值join，它會回傳：

{
  "join": [
    "favorite": [
      "value1",
      "value2"
    ]
  ]
}

因此，當您使用 查詢時join.favorite，它會回傳一個嵌套陣列：

[ ["value1", "value2"] ]

您需要先展平陣列，然后再$in通過$reduce.

{
  $reduce: {
    input: "$join",
    initialValue: [],
    in: {
      $concatArrays: [
        "$$value",
        "$$this.favorite"
      ]
    }
  }
}

完成查詢

db.testA.aggregate([
  {
    $match: {
      $or: [
        {
          "message": {
            $regex: "he"
          }
        },
        {
          "field3": {
            $regex: "s"
          }
        }
      ]
    }
  },
  {
    $lookup: {
      from: "testB",
      localField: "_id",
      foreignField: "favorite",
      as: "join"
    }
  },
  {
    $addFields: {
      favorite: {
        $cond: [
          {
            $in: [
              "$_id",
              {
                $reduce: {
                  input: "$join",
                  initialValue: [],
                  in: {
                    $concatArrays: [
                      "$$value",
                      "$$this.favorite"
                    ]
                  }
                }
              }
            ]
          },
          true,
          false
        ]
      }
    }
  }
])

示例 Mongo Playground

標籤：mongodb 猫鼬 聚合框架

上一篇：Mongoose陣列中的值

下一篇：為什么這個discord.js對mongoose的查詢不起作用？