使用MongoDB联接或聚合多个字段

Question

在将两个MongoDB集合结合在一起时遇到问题。

收藏集A：

   {
    "_id" : ObjectId("5c7e459f875ea5548de25722"),
    "Autos" : [
        {
            "userid" : ObjectId("5c751043b3da4a8e63b7630b"),
            "Size" : "Small",
            "Status" : "New",

        {
            "userid" : ObjectId("5c751043b3da4a8e63b7630b"),
            "Size" : "Medium",
            "Status" : "New",
        },
    ]
    }
    {
        "_id" : ObjectId("5c7e45ce875ea5548de25723"),
        "Ironing" : [
            {
                "userid" : ObjectId("5c751043b3da4a8e63b76xxx"),
                "NumeroCapi" : "4",
                "Status" : "New",

            },
            {
                "userid" : ObjectId("5c751043b3da4a8e63b76xxx"),
                "NumeroCapi" : "4",
                "Status" : "New",
            },
        ]
    }
  }

集合B：

{
    { "_id" : ObjectId("5c751043b3da4a8e63b7630b"), "Username" : "Marco"}
    { "_id" : ObjectId("5c7510d1b3da4a8e63b7630c"), "Username" :"Max"}
} 

我只希望部分成功时就加入userid并仅从信息中提取用户名。其次，我希望此查询加入Collection A中的所有顶级字段，例如Autos，Ironing等。

这是我的查询...部分仅适用于汽车：（

db.rental.aggregate(
    [
        {
            $unwind: "$Autos"
        },

        {
            $lookup:
            {
                from: "user",
                localField: "Autos.userid",
                foreignField: "_id",
                as: "Autos.userinfo"
            }
        },
        {
            $group:
            {
                _id: "$_id",
                 Autos:{$push:"$Autos"}

            }
        },

    ]
).pretty()

结果：

{
    "_id" : ObjectId("5c7e459f875ea5548de25722"),
    "Autos" : [
        {
            "userid" : ObjectId("5c751043b3da4a8e63b7630b"),
            "Size" : "Small",
            "Status" : "New",
            "userinfo" : [
                {
                    "_id" : ObjectId("5c751043b3da4a8e63b7630b"),
                    "Username" : "Marco",
                }
            ]
        },

}

必填结果：

{
    "_id" : ObjectId("5c7e459f875ea5548de25722"),
    "Autos" : [
        {
            "userid" : ObjectId("5c751043b3da4a8e63b7630b"),
            "Size" : "Small",
            "Status" : "New",
            "Username" : "Marco",

            ].
   "Ironing" : [
        {
            "userid" : ObjectId("5c751043b3da4a8e63b7630b"),
            "Status" : "New",
            "Numericapi":5,
            "Username" : "Marco",

            ]

        },

}

一束谢谢...