mongodb query referenced objects inside array - node.js

Question

I'm using mongoose in nodejs. I'm trying to query some fields that contains a list made of referenced objects. I created two schemas
PILOT
var PilotSchema = new mongoose.Schema({
races: [{type: mongoose.Schema.Types.ObjectId, ref: 'Race'}],
});
RACE
var RaceSchema = new mongoose.Schema({
start_ms: Number,
});
Here I wrote only the relevant fields.
In the race schema I have a key start_ms that indicates the date of the start of the race in millisecons, and in the PilotSchema races field I save the references to many races.
What I want to do is:
Take a date in the future ( my_date ) in milliseconds
Retrive all the pilots that have not a race in the interval (my_date - 2_hours, my_date + 2_hours)
I try to do an example for explain better.
My date: Feb 23 2020 - 12:00:00 ( in milliseconds ),
In the pilot field races I have many refences to the RaceSchema and in each refenced object ther is the time of the start of a race.
Now querying the Pilots collection I want to retrieve all the pilots that in they races field have not a race that start during (Feb 23 2020 - 10:00:00 - Feb 23 2020 - 14:00:00)
I tried using this query but didn't work
races: {$not:
{$elemMatch:
{start_ms:
{ "$gt" : min_time, "$lt" : max_time }
}
}
}
Where
min_time, max_time = my_date - 2_hours, my_date + 2_hours
Actually I don't know how to do it, I saw that for retrive a number in an intervall I can use $gt and $lt but I don't understand how to query an array of referenced objects that respect this specific conditions.

Answer 1

You'd have to write an aggregate query for this, finding your reference of races from pilot & filter them based on your condition
Pilot.aggregate([
{
$lookup:{
from:'races',
localField:'races',
foreignField:'_id',
as:'races'
}
},{
$unwind:'$races'
},
{
$match:{
'races.start_ms':{
"$gt" : min_time, "$lt" : max_time
}
}
},{
$group:{
_id:'$_id',
name:{$first:'$name'}
}
}
]);
Assuming that you have name in your pilot schema, you can get list of all such pilots by writing this query