Question

在这种情况下如何获得此结果？

我有一个名为硬币的收藏

[
  {
    "_id" : ObjectId("5dc8c47f638267be1b00e808"),
    "mintTxid" : "abc371bb13034ed6acf96a39e09b22347f0038002eb8a21493032885ba6b77da",
    "address" : "mokZmpYj3vSqghQaZXZ8AGt1oo1HyidLow",
    "spentTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46"
  },
  {
    "_id" : ObjectId("5dc91d0d638267be1b21c2eb"),
    "mintTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46",
    "address" : "mwE7bR8nLF9G1jUY17DzRhdWRrs4fGppvA"
  }
]

我使用$ lookup并加入了自己（spentTxid = mintTxid）

db.getCollection('coins').aggregate([
    { $match: {'address': 'mokZmpYj3vSqghQaZXZ8AGt1oo1HyidLow'}},
    {
        $lookup: {
            from: 'coins',
            localField: 'spentTxid',
            foreignField: 'mintTxid',
            as: 'spents'
        }
    },
    {
        $unwind: {
            path: '$spents',
            preserveNullAndEmptyArrays: true
        }
    }
])

这是结果

{
    "_id" : ObjectId("5dc8c47f638267be1b00e808"),
    "mintTxid" : "abc371bb13034ed6acf96a39e09b22347f0038002eb8a21493032885ba6b77da",
    "address" : "mokZmpYj3vSqghQaZXZ8AGt1oo1HyidLow",
    "spentTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46",
    "spents" : {
        "_id" : ObjectId("5dc91d0d638267be1b21c2eb"),
        "mintTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46",
        "address" : "mwE7bR8nLF9G1jUY17DzRhdWRrs4fGppvA",
    }
}

我如何获得这样的结果？我使用了$ replaceRoot选项，但是该选项仅返回子项。

[
  {
    "_id" : ObjectId("5dc8c47f638267be1b00e808"),
    "mintTxid" : "abc371bb13034ed6acf96a39e09b22347f0038002eb8a21493032885ba6b77da",
    "address" : "mokZmpYj3vSqghQaZXZ8AGt1oo1HyidLow",
    "spentTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46",
  },
  {
    "_id" : ObjectId("5dc91d0d638267be1b21c2eb"),
    "mintTxid" : "fddc7f7c6492e0cf670ff4f96e7aaaeeee3d75c51538a35286b66b6707260b46",
    "address" : "mwE7bR8nLF9G1jUY17DzRhdWRrs4fGppvA",
  }
]

请帮助我...

Answer 1

在聚合之后，添加以下流水线阶段，然后尝试：

  {
    $project: {
      array: {
        $concatArrays: [
          [
            {
              _id: "$$ROOT._id",
              address: "$$ROOT.address",
              mintTxid: "$$ROOT.mintTxid",
              spentTxid: "$$ROOT.spentTxid",

            }
          ],
          [
            "$$ROOT.spents"
          ]
        ]
      }
    }
  },
  {
    $unwind: "$array"
  },
  {
    $replaceRoot: {
      newRoot: "$array"
    }
  }

在项目中，我们创建了一个新数组，其中我们根据需要推送了两个数组
展开数组
将根替换为ROOT中的数据

猫鼬：如何使用汇总和展平子文档列出

1 个答案: