Query item in nested array - mongodb-query

Question

Customer appointments with top level locationId sample data set:
[
{
"locationId": 9999,
"customerAppointments": [
{
"customerId": "1",
"appointments": [
{
"appointmentId": "cbbce566-da59-42c2-8845-53976ba63d56",
"locationName": "Sullivan St"
},
{
"appointmentId": "5f09e2af-ddae-47aa-9f7c-fd1001a9c5e6",
"locationName": "Oak St"
}
]
},
{
"customerId": "2",
"appointments": [
{
"appointmentId": "964a3c1c-ccec-4082-99e2-65795352ba79",
"locationName": "Kellet St"
}
]
},
{
"customerId": "3",
"appointments": []
}
]
},
{
...
},
{
...
}
]
I need to pull out appointment by locationId and customerId and only get the appointment for that customerId e.g
Sample response:
[
{
"appointmentId": "964a3c1c-ccec-4082-99e2-65795352ba79",
"locationName": "Kellet St"
}
]
Tried below query, but it just returns all records for all customers ids (which is kind of expected):
db.getCollection("appointments").find(
{
"locationId" : NumberInt(9999),
"customerAppointments" : {
"$elemMatch" : {
"customerId" : "2"
}
}
}
);
But how can I get just the appointment record for a specific customerId?

Answer 1

When asking this question I was unaware of the older version of MongoDB driver (< v5) so we cannot use the $getField operator.
However, this query seems to work well:
db.getCollection("appointments").aggregate([
{
$match: {
"locationId": NumberInt(9999)
}
},
{
$unwind: "$customerAppointments"
},
{
$match: {
"customerAppointments.customerId": "2"
}
},
{
$project: {
appointments: "$customerAppointments.appointments"
}
}
]);
Yields:
{
"_id" : ObjectId("63eebe95c7a0da54804c1db2"),
"appointments" : [
{
"appointmentId" : "964a3c1c-ccec-4082-99e2-65795352ba79",
"locationName" : "Kellet St"
}
]
}