Mongodb Aggregation :- Get specific fields from $lookup nested array - mongodb

Question

I am trying to get specific fields from the array I got after aggregate, lookup and some cond
Below you can see my query
const attendanceData = await User.aggregate([
{
$match: {
lastLocationId: Mongoose.Types.ObjectId(typeId),
isActive: true,
},
},
{
$project: {
_id: 1,
workerId: 1,
workerFirstName: 1,
workerSurname: 1,
},
},
{
$lookup: {
from: "attendances",
localField: "_id",
foreignField: "employeeId",
as: "attendances",
},
},
{
$set: {
attendances: {
$filter: {
input: "$attendances",
cond: {
$and: [
{
$gte: ["$$this.Date", new Date(fromDate)],
},
{
$lte: ["$$this.Date", new Date(toDate)],
},
{
$eq: ["$$this.createdAs", dataType],
},
{
$eq: ["$$this.status", true],
},
{
$eq: ["$$this.workerType", workerType],
},
],
},
},
},
},
},
{ $skip: 0 },
{ $limit: 10 },
]);
The data as a response i get below
{
"attendanceSheet": [
{
"_id": "60dd77c14524e6c116e16aaa",
"workerFirstName": "FIRST NAME1",
"workerSurname": "SURNAME1",
"workerId": "1",
"attendances": [
{
"_id": "6130781085b5055a15c32f2u",
"workerId": "1",
"workerFullName": "FIRST NAME",
"workerType": "Employee",
"Date": "2022-10-01T00:00:00.000Z",
"createdAs": "ABSENT"
},
{
"_id": "6130781085b5055a15c32f2u",
"workerId": "1",
"workerFullName": "FIRST NAME",
"workerType": "Employee",
"Date": "2022-10-02T00:00:00.000Z",
"createdAs": "ABSENT"
}
]
},
{
"_id": "60dd77c24524e6c116e16c0f",
"workerFirstName": "FIRST NAME2",
"workerSurname": "Surname",
"workerId": "2",
"attendances": [
{
"_id": "6130781a85b5055a15c3455y",
"workerId": "2",
"workerFullName": "FIRST NAME2",
"workerType": "Employee",
"Date": "2022-10-02T00:00:00.000Z",
"createdAs": "ABSENT"
}
]
}
]
}
But I want data something like this below only few fields in not every fields
{
"attendanceSheet": [
{
"_id": "60dd77c14524e6c116e16aaa",
"workerFirstName": "FIRST NAME1",
"workerSurname": "Surname",
"workerId": "1",
"attendances": [
{
"_id": "6130781085b5055a15c32f2u",
"Date": "2022-10-01T00:00:00.000Z",
"createdAs": "ABSENT"
},
{
"_id": "6130781085b5055a15c32f2u",
"Date": "2022-10-02T00:00:00.000Z",
"createdAs": "ABSENT"
}
]
},
{
"_id": "60dd77c24524e6c116e16c0f",
"workerFirstName": "FIRST NAME2",
"workerSurname": "Surname",
"workerId": "2",
"attendances": [
{
"_id": "6130781a85b5055a15c3455y",
"Date": "2022-10-02T00:00:00.000Z",
"createdAs": "ABSENT"
}
]
}
]
}

Answer 1

You could simplify/refactor your aggregation pipeline by putting all the matching in a "$lookup" "pipeline".
db.users.aggregate([
{
"$match": {
"lastLocationId": ObjectId("0123456789abcdef01234567"),
"isActive": true
}
},
{
"$project": {
"workerId": 1,
"workerFirstName": 1,
"workerSurname": 1
}
},
{
"$lookup": {
"from": "attendances",
"localField": "_id",
"foreignField": "employeeId",
"as": "attendances",
// do all the matching here
"pipeline": [
{
"$match": {
"Date": {
// fromDate, toDate
"$gte": ISODate("2022-09-01T00:00:00Z"),
"$lte": ISODate("2022-09-30T23:59:59Z")
},
// dataType
"createdAs": "ABSENT",
"status": true,
// workerType
"workerType": "Employee"
}
},
{
"$project": {
"Date": 1,
"createdAs": 1
}
}
]
}
},
{$skip: 0},
{$limit: 10}
])
Try it on mongoplayground.net.

Answer 2

One option to get from what you have to the requested output is to $map and $reduce:
db.collection.aggregate([
{
$set: {
attendanceSheet: {
$map: {
input: "$attendanceSheet",
as: "external",
in: {
$mergeObjects: [
"$$external",
{
attendances: {
$reduce: {
input: "$$external.attendances",
initialValue: [],
in: {
$concatArrays: [
"$$value",
[
{
_id: "$$this._id",
createdAs: "$$this.createdAs",
Date: "$$this.Date"
}
]
]
}
}
}
}
]
}
}
}
}
}
])
See how it works on the playground example

Answer 3

The below modification worked for me
const attendanceData = await User.aggregate([
{
$match: {
lastLocationId: Mongoose.Types.ObjectId(typeId),
isActive: true,
},
},
{
$project: {
_id: 1,
workerId: 1,
workerFirstName: 1,
workerSurname: 1,
},
},
{
$lookup: {
from: "attendances",
localField: "_id",
foreignField: "employeeId",
as: "attendances",
},
},
{
$set: {
attendances: {
$filter: {
input: "$attendances",
cond: {
$and: [
{
$gte: ["$$this.Date", new Date(fromDate)],
},
{
$lte: ["$$this.Date", new Date(toDate)],
},
{
$eq: ["$$this.createdAs", dataType],
},
{
$eq: ["$$this.status", true],
},
{
$eq: ["$$this.workerType", workerType],
},
],
},
},
},
},
},
{
$set: {
attendances: {
$reduce: {
input: "$attendances",
initialValue: [],
in: {
$concatArrays: [
"$$value",
[
{
_id: "$$this._id",
createdAs: "$$this.createdAs",
Date: "$$this.Date",
},
],
],
},
},
},
},
},
{ $skip: 0 },
{ $limit: 10 },
]);