如何使用 lambda 函数在 mongodb 中的两个集合之间进行多个连接？

Question

我有两个集合 1) user_posts 2)user_profile。查找以下收集数据供您参考。

1) user_posts 集合

_id :ObjectId("5d519f861c9d4400005ebd1b")
userid : ObjectId("5d518caed55bc00001d235c1")
media : "hello.jpg"
type : "jpg"
created : " "
modified : " "
like : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           status : "like"
       1 : Object
           userid : ObjectId("5d518da6d55bc00001d235c2")
           status : "happy"
comment : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           comment : "hello"
       1 : Object
           userid : ObjectId("5d518da6d55bc00001d235c2")
           comment : "welcome"
share : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           status : "shared"
       1 : Object
           userid : ObjectId("5d518da6d55bc00001d235c2")
           status : "shared"

2) User_profile 集合

 _id : ObjectId("5d518caed55bc00001d235c1")
 username : "ramesh",
 photo :  " ",
 created : " ",
 modified : " "

 _id : ObjectId("5d518da6d55bc00001d235c2")
 username : "shekar",
 photo :  " ",
 created : " ",
 modified : " "

现在我尝试从 lambda 函数中的 user_profile 获取配置文件详细信息。但我没有得到细节。找到下面的 lambda 函数代码。

def lambda_handler(event, context):

print("Received event: " + json.dumps(event, indent=1))

user_posts = db.user_posts

Userid = event['userid']
uid = ObjectId(Userid)

dispost = list(user_posts.aggregate([{
"$match" : { "userid" : uid }
},
{ "$graphLookup" : 
     {
       "from" : "user_profile",
       "startWith" : "$like.userid",
       "connectFromField" : "like.userid",
       "connectToField" : "_id",
       "as" : "userdetails"
     }
},
{ "$graphLookup" : 
     {
       "from" : "user_profile",
       "startWith" : "$comment.userid",
       "connectFromField" : "comment.userid",
       "connectToField" : "_id",
       "as" : "userdetails1"
     }
}
{ "$graphLookup" : 
     {
       "from" : "user_profile",
       "startWith" : "$share.userid",
       "connectFromField" : "share.userid",
       "connectToField" : "_id",
       "as" : "userdetails2"
     }
}
]))     
disair = json.dumps(dispost, default=json_util.default)
return json.loads(disair)

但我没有得到输出。我需要像下面这样的输出。

_id :ObjectId("5d519f861c9d4400005ebd1b")
userid : ObjectId("5d518caed55bc00001d235c1")
username : "ramesh"
photo : " ",
media : "hello.jpg"
type : "jpg"
created : " "
modified : " "
like : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           status : "like"
           username : "ramesh"
           photo : " "
       1 : Object
           username : "shekar"
           photo : " "
           userid : ObjectId("5d518da6d55bc00001d235c2")
           status : "happy"
           username : "shekar"
           photo : " "
comment : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           comment : "hello"
           username : "ramesh"
           photo : " "
       1 : Object
           userid : ObjectId("5d518da6d55bc00001d235c2")
           comment : "welocme"
           username : "shekar"
           photo : " "
share : Array
       0 : Object
           userid : ObjectId("5d518caed55bc00001d235c1")
           status : "shared"
           username : "ramesh"
           photo : " "
       1 : Object
           userid : ObjectId("5d518da6d55bc00001d235c2")
           status : "shared"
           username : "shekar"
           photo : " "

你能帮我解决问题吗？提前致谢。

Answer 1

请检查：

db.collection("user_posts").aggregate(
{ $match: {"userid" : uid}},
{ $unwind: '$like' },
{ $lookup: { from: "users", localField: "like.userid", foreignField: "_id", as: 
"users" }},
{ $group: {
    _id: "$_id",
    like: { $push: { $mergeObjects: ['$like', { $arrayElemAt: [ "$users", 0 ] } ]}},
    data: { $first: "$$ROOT" }
}},
{ $replaceRoot: { newRoot: { $mergeObjects: ['$data', { like: "$like"} ]} } },
{ $unwind: '$comment' },
{ $lookup: { from: "users", localField: "comment.userid", foreignField: "_id", as: 
 "users" }},
{ $group: {
    _id: "$_id",
        comment: { $push: { $mergeObjects: ['$comment', { $arrayElemAt: [ "$users", 0 
 ] } ]}},
        data: { $first: "$$ROOT" }
}},
{ $replaceRoot: { newRoot: { $mergeObjects: ['$data', { comment: "$comment"} ]} } },
{ $unwind: '$share' },
{ $lookup: { from: "users", localField: "share.userid", foreignField: "_id", as: 
"users" }},
{ $group: {
    _id: "$_id",
    share: { $push: { $mergeObjects: ['$share', { $arrayElemAt: [ "$users", 0 ] } 
]}},
    data: { $first: "$$ROOT" }
}},
{ $replaceRoot: { newRoot: { $mergeObjects: ['$data', { share: "$share"} ]} } },
{ $project: { users: 0 }}
)

您将获得输出，根据您的要求更改项目聚合中的添加/删除字段名称

Answer 2

请检查：

    db.user_posts.aggregate([{ $match: { _id: ObjectId("5d519f861c9d4400005ebd1b") } }, {
    $lookup:
    {
        from: "user_profile",
        let: { userIdToBeCompared: "$userid", like: '$like', comment: '$comment', share: '$share' },
        pipeline: [
            {
                $match:
                {
                    $expr:
                    {

                        $or:
                            [
                                { $eq: ["$_id", "$$userIdToBeCompared"] },
                                { $in: ["$_id", "$$like.userid"] },
                                { $in: ["$_id", "$$comment.userid"] },
                                { $in: ["$_id", "$$share.userid"] }
                            ]
                    }
                }
            }

        ],
        as: "data"
    }
}])

好吧，您的需求中有太​​多事情要做，而对于您当前的数据结构，从您的数据库层实现您的所有需求可能不是一件容易的事情和一个好主意，所以在这里最终响应 data 将拥有满足您需求的所有映射，将其添加到您的代码中，并根据用户 ID 为每个部分获取所需的详细信息，就我所尝试的而言，我认为这将是实现的理想方案！