MongoDB aggregation lookup objects in specific date range - mongodb

Question

I have some users and orders made by them:
db={
orders: [
{
"_id": "wJNEiSYwBd5ozGtLX",
"orderId": 52713,
"retailerId": 1320,
"createdAt": ISODate("2020-01-31T04:34:13.790Z"),
"status": "closed"
},
{
"_id": "wJNEiSYwBd5ozGtLX2",
"orderId": 52714,
"retailerId": 1320,
"createdAt": ISODate("2021-03-31T04:34:13.790Z"),
"status": "closed"
}
],
users: [
{
"_id": "2gSznevqwkGTxLRvL",
"createdAt": ISODate("2018-04-10T08:33:13.455Z"),
"username": "retailer#gmail.com",
"info": {
"retailerId": 1320,
},
"settings": {},
"status": "active",
}
]
}
If I try to aggregate orders into users:
db.users.aggregate([
{
"$lookup": {
"from": "orders",
"localField": "info.retailerId",
"foreignField": "retailerId",
"as": "orders"
}
},
])
I can get all orders merged into users like this:
[
{
"_id": "2gSznevqwkGTxLRvL",
"createdAt": ISODate("2018-04-10T08:33:13.455Z"),
"info": {
"retailerId": 1320
},
"orders": [
{
"_id": "wJNEiSYwBd5ozGtLX",
"createdAt": ISODate("2020-01-31T04:34:13.79Z"),
"orderId": 52713,
"retailerId": 1320,
"status": "closed"
},
{
"_id": "wJNEiSYwBd5ozGtLX2",
"createdAt": ISODate("2021-03-31T04:34:13.79Z"),
"orderId": 52714,
"retailerId": 1320,
"status": "closed"
}
],
"settings": {},
"status": "active",
"username": "retailer#gmail.com"
}
]
But I want to only merge orders from last month, not all orders into users.
How can I specify the date range?
https://mongoplayground.net/p/mZlDHQf2thN

Answer 1

Demo - https://mongoplayground.net/p/-hjGipqQPJq
https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/#join-conditions-and-uncorrelated-sub-queries
To perform uncorrelated subqueries between two collections as well as allow other join conditions besides a single equality match, the $lookup stage has the following syntax:
Use $lookup in the pipeline style -
db.users.aggregate([
{
"$lookup": {
"from": "orders",
"let": { "rId": "$info.retailerId" },
"pipeline": [
{
$match: {
$expr: { $eq: [ "$retailerId","$$rId" ] },
createdAt: { $gte: ISODate("2021-03-01T00:00:00.000Z"), $lt: ISODate("2021-04-01T00:00:00.000Z") } // write date range query here
}
}
],
"as": "orders"
}
}
])