对 Mongodb 嵌套聚合有疑问

Question

我正在使用 aggregate 创建一个函数。我正在使用查找绑定三个数据库。下面这个函数组成的时候，有没有办法绑定A的数据和C的数据？

A.aggregate([
    {
      $lookup: {
        from: "B",
        let: { aid: "$aid" },
        pipeline: [
          { $match: { $expr: { $in: ["$_id", "$$aid"] } } },
          {
            $lookup: {
              from: "C",
              let: { bid: "$bid" },
              pipeline: [
                {
                  $match: {
                    $expr: {
                      $eq: ["$$bid, "$aid"],
                    },
                  },
                },
              ],
              as: "list",
            },
          },
        ...
  ])

Answer 1

我对此有了更多的了解，并且通过执行以下操作找到了我正在寻找的结果：

A.aggregate([
    {
      $lookup: {
        from: "B",
        let: { bid: "$bid", aid: "$aid" },
        pipeline: [
          { $match: { $expr: { $in: ["$_id", "$$bid"] } } },
          {
            $lookup: {
              from: "C",
              localField: "_id",
              foreignField: "cid",
              as: "list",
            },
          },
          {
            $unwind: "$list",
          },
          // One More Match
          {
            $match: { $expr: { $eq: ["$$aid", "$list.aid"] } },
          },
          {
            $addFields: {
              list: "$list.clist",
            },
          },
        ],
        as: "blist",
      },
    },
  ])

对 Mongodb 嵌套聚合有疑问

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