Filter and update embedded Array in mongodb mongoose - mongodb

Question

The MongoDb model looks like this :
{
"_id": {
"$oid": "5ee269c949c9d58970528d1e"
},
"parent": [
{
"_id": {
"$oid": "5ee269c949c9d58970528d1d"
},
"uType": "parent",
"fName": "p1",
"lName": "p1",
"num": "123"
}
],
"child": [
{
"_id": {
"$oid": "5ee269c949c9d58970528d1c"
},
"uType": "child",
"fName": "c1",
"lName": "c1",
"num": "8963",
"email": "c1#gmail.com",
"gender": "male"
}
]
}
I have an incoming object that looks like this -
{
"uType":"child",
"fName": "c2",
"lName": "c2",
"num": "98733",
"email": "c2#gmail.app",
"invite": {
"uType": "parent",
"fName": "p1",
"lName": "p1",
"num": "123"
}
}
I have to filter for the incoming object such that I get the response like below- which means for the incoming object, there is a matching parent but there is not a matching child.
Tried using $or and provided multiple conditions but every time ended up getting a record in child array. I gave it a shot using aggregate as well but could not find a possible solution. Can someone tell me what is the best way to do this?
{
"_id": {
"$oid": "5ee269c949c9d58970528d1e"
},
"parent": [
{
"isActive": false,
"_id": {
"$oid": "5ee269c949c9d58970528d1d"
},
"uType": "parent",
"fName": "p1",
"lName": "p1",
"num": "123"
}
],
"child": [ ]
}
UPDATE: Tried using projection, but still no luck -
Model.aggregate([
{
$project: {
child: {
$filter: {
input: "$child",
as: "ch",
cond: { $eq: ["$ch.num", this.num] }
}
}
}
}
])

Answer 1

Actually, you are so close to the solution, if you use "$$ch.num" instead of "$ch.num" it should work.
const match = {
"uType":"child",
"fName": "c2",
"lName": "c2",
"num": "98733",
"email": "c2#gmail.app",
"invite": {
"uType": "parent",
"fName": "p1",
"lName": "p1",
"num": "123"
}
}
Model.aggregate([
{
$match: {
$or: [
{
"parent.num": match.invite.num
},
{
"child.num": match.num
}
]
}
},
{
$project: {
parent: {
$filter: {
input: "$parent",
as: "p",
cond: {
$eq: [
"$$p.num",
match.invite.num
]
}
}
},
child: {
$filter: {
input: "$child",
as: "ch",
cond: {
$eq: [
"$$ch.num",
match.num
]
}
}
}
}
}
])
But you can do something similar without aggregation, but you will not get an empty array when there is no match, you will just don't get the key.
Model.find({
$or: [
{
"parent.num": match.invite.num
},
{
"child.num": match.num
}
]
},
{
parent: {
$elemMatch: {
num: match.invite.num
},
},
child: {
$elemMatch: {
num: match.num
}
}
})