How to combined two output in lambda function using mongodb?

Question

I have two collection 1) profile ,2) posts find the below pic for your reference. user_prfoile collection

In the lambda function, when i passed the userid, then we will get the userid revlevant data display. but i need user details in feelings array.

I tried with the below code, but i get the empty output

def lambda_handler(event, context):

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


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

dispost = list( db.user_posts.aggregate([{ "$match" : { "userid" : uid } }, 
{ "$unwind" : "$user_profile" },
{"$lookup":
    {
        "from" : 'user_profile',
        "localField" : 'feelings.userid',
        "foreignField" : '_id',
        "as" : 'user_details'
    }
},  
{ "$addFields" : { "user_details.feelings.username" : "$user_profile.username", "user_details.feelings.photo" : "$user_profile.photo"}},
{ "$group" :  { 
            "_id" : "$_id", 
            "user_profile" : { 
                "$push" : { 
                        "$arrayElemAt" :  ["$user_details", 0]
}}}}, 
{ "$project" : { "_id" : "$_id", "userid" : 1, "type" : 1, "feelings" : 1 }}
]))
disair = json.dumps(dispost, default=json_util.default)
return json.loads(disair)

I get an empty output.

I need output like this below.

_id :
userid : 
type : 
location :
feelings : 
   [ {userid : objectid(""),
     username : "nipun",
     photo : " "},
     {userid : objectid(""),
     username : "ramesh",
     photo : " "}
   ]

in feelings array , i need user details from user_profile collection based on userid in feelings array.

you've to do $unwind on feelings array of user_posts. Please provide documents in text format rather than images. — whoami - fakeFaceTrueSoul
– whoami - fakeFaceTrueSoul, Commented Aug 7, 2019 at 15:50

whoami - fakeFaceTrueSoul · Accepted Answer · 2019-08-07 16:32:06Z

1

Ok, there are couple of issues with that aggregation query, keeping most of it as is, I've modified it to work, as of now please try this and make any changes needed :

db.getCollection('user_posts').aggregate([{ "$match": { "userid": uid } },
{ "$unwind": "$feelings" },
{
    "$lookup":
    {
        "from": 'user_profile',
        "localField": 'feelings.userid',
        "foreignField": '_id',
        "as": 'feelings'
    }
},
{
    "$group": {
        "_id": "$_id", userPost: { "$first": "$$CURRENT" }, "feelings": {
            "$push": { "$arrayElemAt": ["$feelings", 0] }
        }
    }
}, { "$project": { userid: '$userPost.userid', type: '$userPost.type', "feelings": 1 } }
])

answered Aug 7, 2019 at 16:32

whoami - fakeFaceTrueSoul

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14 Comments

Ramesh Reddy Over a year ago

Thank you so much bro. it's working fine. I have one small query bro, In feeling array i need username and photo only from user_profile collection. How can i remove other columns.

whoami - fakeFaceTrueSoul Over a year ago

@RameshReddy : Quick thing is to do "feelings.username": 1, "feelings.photo": 1 in $project, or if you really think there are a lot of fields to be added then use $addFields, while on mapping if possible only map to necessary fields !!

Ramesh Reddy Over a year ago

bro above solutions working , i have one more last query. In user_post, i have userid right. i need username, photo based on userid. I tried one more join but it is not working.

whoami - fakeFaceTrueSoul Over a year ago

@RameshReddy : that’s what this query does, do you see any issue in it ?

Ramesh Reddy Over a year ago

no bro, my query is we have two userid in document of user_posts collection. previously we are working on feelings userid. now i need outside userid user details along with feelings userid user details.

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