Mongo Query to get a result - node.js

Question

My mongo collection name tests and whose having the following documents in it.
[
{
"title": "One",
"uid": "1",
"_metadata": {
"references": [
{
"uid": "2"
},
{
"asssetuid": 10
}
]
}
},
{
"title": "Two",
"uid": "2",
"_metadata": {
"references": [
{
"uid": "3"
},
{
"asssetuid": 11
}
]
}
},
{
"title": "Three",
"uid": "3",
"_metadata": {
"references": []
}
}
]
And I want the result in the following format (for uid:1)
[
{
"title": "One",
"uid": 1,
"_metadata": {
"references": [
{
"asssetuid": 10
},
{
"asssetuid": 11
},
{
"title": "Two",
"uid": "2",
"_metadata": {
"references": [
{
"title": "Three",
"uid": "3"
}
]
}
}
]
}
}
]
for uid:2 I want the following result
[
{
"title": "Two",
"uid": 2,
"_metadata": {
"references": [
{
"asssetuid": 11
},
{
"title": "Three",
"uid": "3"
}
]
}
}
]
Which query I used here to get a respected result. according to its uid. here I want the result in the parent-child relationship. is this possible using MongoDB graph lookup query or any other query that we can use to get the result. Please help me with this.
New Type Output
[{
"title": "One",
"uid": 1,
"_metadata": {
"assets": [{
"asssetuid": 10,
"parent": 1
}, {
"asssetuid": 11,
"parent": 2
}],
"entries": [{
"title": "Two",
"uid": "2",
"parent": 1
}, {
"title": "Three",
"uid": "3",
"parent": 2
}]
}
}]

Answer 1

Mongo supports the automatic reference resolution using $ref but for that, you need to change your schema a little and resolve resolution is only supported by some drivers.
You need to store your data in this format:
[
...
{
"_id": ObjectId("5a934e000102030405000000"),
"_metadata": {
"references": [
{
"$ref": "collection",
"$id": ObjectId("5a934e000102030405000001"),
"$db": "database"
},
{
"asssetuid": 10
}
]
},
"title": "One",
"uid": "1"
},
....
]
For more details on $ref refer to official documentation: label-document-references
OR
you can resolve the reference using the $graphLookup but the only problem with the $graphlookup is that you will lose the assetuid. Here is the query and it will resolve references and give output in flat map
db.collection.aggregate([
{
$match: {
uid: "1"
}
},
{
$graphLookup: {
from: "collection",
startWith: "$_metadata.references.uid",
connectFromField: "_metadata.references.uid",
connectToField: "uid",
depthField: "depth",
as: "resolved"
}
},
{
"$addFields": {
"references": "$resolved",
"metadata": [
{
"_metadata": "$_metadata"
}
]
}
},
{
"$project": {
"references._metadata": 0,
}
},
{
"$project": {
"references": "$references",
"merged": {
"$concatArrays": [
"$metadata",
"$resolved"
]
}
}
},
{
"$project": {
results: [
{
merged: "$merged"
},
{
references: "$references"
}
]
}
},
{
"$unwind": "$results"
},
{
"$facet": {
"assest": [
{
"$match": {
"results.merged": {
"$exists": true
}
}
},
{
"$unwind": "$results.merged"
},
{
"$unwind": "$results.merged._metadata.references"
},
{
"$match": {
"results.merged._metadata.references.asssetuid": {
"$exists": true
}
}
},
{
"$project": {
_id: 0,
"asssetuid": "$results.merged._metadata.references.asssetuid"
}
}
],
"uid": [
{
"$match": {
"results.references": {
"$exists": true
}
}
},
{
"$unwind": "$results.references"
},
{
$replaceRoot: {
newRoot: "$results.references"
}
}
]
}
},
{
"$project": {
"references": {
"$concatArrays": [
"$assest",
"$uid"
]
}
}
}
])
Here is the link to the playground to test it: Mongo Playground