grouping result from multiple queries and aggregating result mongo - mongodb

Question

I'm new to mongo and I have a document that has an array with the ids of all it's related documents. I need to fetch the document with all it's relateds in a single query. For the moment I fetch the document and I query separatly each of it's related document with there ids.
all my documents are on the same collection documents_nodes and look like so:
{
"id": "document_1",
"name": "flask",
"relateds": [
"document_2",
"document_3",
"document_4"
],
"parents": [
"document1_1"
]
}
The first query is to get the initial document
db.documents_nodes.find({id: document_1})
And then I query it's relateds with a second query
db.documents_nodes.aggregate([{
$match: {
$and: [{
id: {
$in: ["document_2", "document_3", "document_2"]
}
}]
}
}])
is there a way to combine the two queries, I tried this but it doesn't work
db.documents_nodes.aggregate([
{
$match: {
uri: "https://opus.adeo.com/LMFR_prod/3206"
}
},
{
$addFields: {
newRelateds:
{
$match: {
id: {
$in: [ "$relateds" ]
}
}
}
}
}
])
"errmsg" : "Unrecognized expression '$match'",
"code" : 168,
"codeName" : "InvalidPipelineOperator"

Answer 1

I have found a way to do it, in case someone has the same need.
I used the $unwind to flatten the array of documents and then used the $lookup to fetch the documents by their ids and finally I group the result on a new key.
[{
$match: {
id: "document_1"
}
}, {
$unwind: {
path: '$relateds',
}
}, {
$lookup: {
from: 'documents_nodes',
localField: 'relateds',
foreignField: 'id',
as: 'newRelateds'
}
}, {
$group: {
_id: '$id',
relateds: {
'$push': '$newRelateds'
}
}
}]