$unwind, $aggregation manipulation in mongodb nodejs - mongodb

Question

please check this query
db.billsummaryofthedays.aggregate([
{
'$match': {
'userId': ObjectId('5e43de778b57693cd46859eb'),
'adminId': ObjectId('5e43e5cdc11f750864f46820'),
'date': ISODate("2020-02-11T16:30:00Z"),
}
},
{
$lookup:
{
from: "paymentreceivables",
let: { userId: '$userId', adminId: '$adminId' },
pipeline: [
{
$match:
{
paymentReceivedOnDate:ISODate("2020-02-11T16:30:00Z"),
$expr:
{
$and:
[
{ $eq: ["$userId", "$$userId"] },
{ $eq: ["$adminId", "$$adminId"] }
]
}
}
},
{ $project: { amount: 1, _id: 0 } }
],
as: "totalPayment"
}
}, {'$unwind':'$totalPayment'},
{ $group:
{ _id:
{ date: '$date',
userId: '$userId',
adminId: '$adminId' },
totalBill:
{
$sum: '$billOfTheDay'
},
totalPayment:
{
$sum: '$totalPayment.amount'
}
}
},
}
}])
this is the result i am getting in the shell
{
"_id" : {
"date" : ISODate("2020-02-11T18:30:00Z"),
"userId" : ObjectId("5e43de778b57693cd46859eb"),
"adminId" : ObjectId("5e43e5cdc11f750864f46820")
},
"totalBill" : 1595.6799999999998,
"totalPayments" : 100
}
now this is not what i expected,i assume due to {'$unwind':'$totalPayment'} it takes out all the values from the array and because of which every document is getting counted 2 times. When i remove {'$unwind':'$totalPayment'} then totalBill sum turns out to be correct but totalPayment is 0.
I have tried several other ways but not able to achieve the desired result
Below are my collections:
// collection:billsummaryofthedays//
{
"_id" : ObjectId("5e54f784f4032c1694535c0e"),
"userId" : ObjectId("5e43de778b57693cd46859eb"),
"adminId" : ObjectId("5e43e5cdc11f750864f46820"),
"date" : ISODate("2020-02-11T16:30:00Z"),
"UID":"acex01"
"billOfTheDay" : 468,
}
{
"_id" : ObjectId("5e54f784f4032c1694535c0f"),
"UID":"bdex02"
"userId" : ObjectId("5e43de778b57693cd46859eb"),
"adminId" : ObjectId("5e43e5cdc11f750864f46820"),
"date" : ISODate("2020-02-11T16:30:00Z"),
"billOfTheDay" : 329.84,
}
// collection:paymentreceivables//
{
"_id" : ObjectId("5e43e73169fe1e3fc07eb7c5"),
"paymentReceivedOnDate" : ISODate("2020-02-11T16:30:00Z"),
"adminId" : ObjectId("5e43e5cdc11f750864f46820"),
"userId" : ObjectId("5e43de778b57693cd46859eb"),
"amount" : 20,
}
{
"_id" : ObjectId("5e43e73b69fe1e3fc07eb7c6"),
"paymentReceivedOnDate" : ISODate("2020-02-11T16:30:00Z"),
"adminId" : ObjectId("5e43e5cdc11f750864f46820"),
"userId" : ObjectId("5e43de778b57693cd46859eb"),
"amount" : 30,
}
desired result should be totalBill:797.83 i.e[468+329.84,] and totalPayment:50 i.e[30+20,] but i am getting double the expected result and even if i am able to calculate one of the value correctly the other one result 0.How to tackle this??

Answer 1

Since you've multiple documents with same data in billsummaryofthedays collection then you can group first & then do $lookup - that way JOIN between two collections would be 1-Vs-many rather than many-Vs-many as like it's currently written, So you can try below query for desired o/p & performance gains :
db.billsummaryofthedays.aggregate([
{
"$match": {
"userId": ObjectId("5e43de778b57693cd46859eb"),
"adminId": ObjectId("5e43e5cdc11f750864f46820"),
"date": ISODate("2020-02-11T16:30:00Z"),
}
},
{
$group: {
_id: {
date: "$date",
userId: "$userId",
adminId: "$adminId"
},
totalBill: {
$sum: "$billOfTheDay"
}
}
},
{
$lookup: {
from: "paymentreceivables",
let: {
userId: "$_id.userId",
adminId: "$_id.adminId"
},
pipeline: [
{
$match: {
paymentReceivedOnDate: ISODate("2020-02-11T16:30:00Z"),
$expr: {
$and: [
{
$eq: [
"$userId",
"$$userId"
]
},
{
$eq: [
"$adminId",
"$$adminId"
]
}
]
}
}
},
{
$project: {
amount: 1,
_id: 0
}
}
],
as: "totalPayment"
}
},
{
$addFields: {
totalPayment: {
$reduce: {
input: "$totalPayment",
initialValue: 0,
in: {
$add: [
"$$value",
"$$this.amount"
]
}
}
}
}
}
])
Test : MongoDB-Playground