Mongodb aggregate on two collections based on geopoint - mongodb

Question

I have two collections
person
{
"name": "Mike",
"age": 42,
"address": {
"location": {"type": "Point", "coordinates": [12.3456, 78.9101]}
}
}
restaurant
{
"name": "Bistro",
"type": ["Maxican", "Italian"],
"location": {"type": "Point", "coordinates": [12.3555, 78.9333]}
}
I've created spherical indexes on both collections
db.person.createIndex({"address.location": "2dsphere"})
db.restaurant.createIndex({"location": "2dsphere"})
Now I want to find all the restaurants near to a person using lat/long in both collections.
for e.g find all the restaurants within 10KM of a person. result will look like below
{
"name": "Mike",
"age": 42,
"address": {
"location": {"type": "Point", "coordinates": [12.3456, 78.9101]}
},
"nearby_restaurants": [{"name": "Bistro", "distance": 5.3}] // this means bistro is 5.3 KM away from this person
}
Notice that, I'm only using name field from restaurant collection and an additional field distance which will be calculated after the query.
I want to do this for all person. so basically for each person, i have to scan the whole restaurant collection every time.
To achieve this I thought of using lookup with aggregate, something like below
db.person.aggregate([
{
$lookup: {
from: "restaurant",
let: {"personPoint": "$address.location"},
as: "nearby_restaurants",
pipeline: [
{
$geoNear: {
near: "$$personPoint",
spherical: true,
distanceField: "distance",
maxDistance: 10 * 1000, // within 10 KM
distanceMultiplier: 0.001 // get the result in KM
}
},
{
$unwind: "$location"
},
]
}
},
{
$unwind: {
path: "$nearby_restaurants",
preserveNullAndEmptyArrays: true
}
}
])
This doesnt work at all. I get this error: $geoNear requires a 'near' option as an Array"
I tried to look at different sources but couldnt understand and fix the error.
PS: If currently, it's not possible through lookups/aggregate, how can we achieve the same through looping over each person's document?