Mongoose aggregate internal lookup grouping by field - mongodb

Question

I'm trying to group all distinct fields and then lookup into another table , the problem is that I'm adding too many results for the same user inside the lookup, so I wonder how can I group those results internally and then in the next stage add another lookup to a different table.
Currently I have the following code:
Post.aggregate([
{ "$group" : {"_id" : { "id_fanpage": "$id_fanpage" },"total": { $sum: 1 } } },
{
"$lookup": {
"from": "v3_post_reaccion_angry",
"localField": "_id.id_fanpage",
"foreignField": "id_fanpage",
"as": "resultingAngries"
}
},
{
"$lookup": {
"from": "v3_post_reaccion_compartir",
"localField": "_id.id_fanpage",
"foreignField": "id_fanpage",
"as": "resultingCompartir"
}
}
]).exec(function(err, results){
console.log(results);
return results
}).then(success(res))
What I'm trying to do is distinct Post rows by "id_fanpage", then join another table by that returned id_fanpage, which is basically working as expected, the results are this:
{
"_id": {
"id_fanpage": "5a63a96d1aa940ca0ada1c82"
},
"total": 831,
"resultingAngries": [
{
"_id": "5a71ccda1aa940dd154caf83",
"id_post": "5a71ccda1aa940dd154caf82",
"id_fanpage": "5a63a96d1aa940ca0ada1c82",
"facebook_usuario_id": 345346565665,
"facebook_usuario_nombre": "AAAAAAAAAAAAAAAAA"
},
{
"_id": "5a71cd6b1aa940dd154ddb43",
"id_post": "5a71cd6b1aa940dd154ddb40",
"id_fanpage": "5a63a96d1aa940ca0ada1c82",
"facebook_usuario_id": "44444444444444444",
"facebook_usuario_nombre": "XXXXXXXXXXXXXXXX"
},
{
"_id": "5a71d7f61aa940dd156b60f4",
"id_post": "5a71d7f61aa940dd156b60e9",
"id_fanpage": "5a63a96d1aa940ca0ada1c82",
"facebook_usuario_id": "asdf12345232421",
"facebook_usuario_nombre": "YYYYYYYYYYYYYY"
},
{
"_id": "5a71cde11aa940dd154ec514",
"id_post": "5a71cde11aa940dd154ec513",
"id_fanpage": "5a63a96d1aa940ca0ada1c82",
"facebook_usuario_id": "asdf2345234555",
"facebook_usuario_nombre": "ZZZZZZZZZZZZZZ"
},
{
"_id": "5a71cdcb1aa940dd154e917a",
"id_post": "5a71cdcb1aa940dd154e9178",
"id_fanpage": "5a63a96d1aa940ca0ada1c82",
"facebook_usuario_id": "44444444444444444",
"facebook_usuario_nombre": "XXXXXXXXXXXXXXX"
}
]
}
Now the problem is, I want to group all results inside resultingAngries by facebook_usuario_id and also be able to add the the same to the next lookup, but as far as I know I cannot use a group after the first lookup without affecting the next lookup.
So the result should be:
{
"_id": {
"id_fanpage": "5a63a96d1aa940ca0ada1c82"
},
"total": 831,
"resultingAngries": [
{
"_id": "this is my user id 1111111111",
"count": N,
},
{
"_id": "this is my user id 2222222222",
"count": Y,
}
],
"resultingLikes": [
{
"_id": "this is my user id 1111111111",
"count": N,
},
{
"_id": "this is my user id 2222222222",
"count": Y,
}
],
},
{
"_id": {
"id_fanpage": "5a63a96d1aa942345wedf23455s"
},
"total": 20,
"resultingLikes": [
{
"_id": "this is my user id 1111111111",
"count": N,
},
{
"_id": "this is my user id 2222222222",
"count": Y,
}
],
},
"resultingAngries": [
{
"_id": "this is my user id 1111111111",
"count": N,
},
{
"_id": "this is my user id 2222222222",
"count": Y,
}
],
And so on.
I already have seen aggregate, and lookups and not sure if $addToSet can make it, because I cannot group internally so far so applying addToSet is giving me hard times. Help would be appreciate.

Answer 1

Insert below three stages between your $lookup's.
The below steps $unwind resultingAngries array followed by first $group to count the distinct combination of facebook_usuario_id & id_fanpage and second $group to $push the count and facebook_usuario_id back into resultingAngries array.
{"$unwind":"$resultingAngries"},
{"$group":{
"_id":{
"id_fanpage":"$_id.id_fanpage",
"facebook_usuario_id":"$resultingAngries.facebook_usuario_id"
},
"total":{"$first":"$total"},
"count":{"$sum":1}
}},
{"$group":{
"_id":{"id_fanpage":"$_id.id_fanpage"},
"total":{"$first":"$total"},
"resultingAngries":{
"$push":{
"_id":"$_id.facebook_usuario_id",
"count":"$count"
}
}
}}