Mongoose query on subdocument returns array of other subdocument using projection - mongodb

Question

Update: I am looking for an answer that works within mongodb projection: https://docs.mongodb.com/manual/reference/method/db.collection.findOne/#definition
I am trying to filter a query on a subdocument using projection so that it only returns a specific array. But when filtering the result also includes an array of another subdocument. When I don't filter it only returns the found document.
I tried different filtering options including and excluding positional elements, but can't get the desired return.
Mongoose schema
const stationSchema = new mongoose.Schema({
mac: String,
stationName: String,
syncReadings: Boolean,
temperature: Array,
humidity: Array,
measures: [{
date: Date,
temperature: Number,
humidity: Number
}],
lastUpdated: Date
});
// Define user schema
var userSchema = mongoose.Schema({
local : {
email : String,
password : String
},
facebook : {
id : String,
token : String,
name : String,
email : String
},
twitter : {
id : String,
token : String,
displayName : String,
username : String
},
google : {
id : String,
token : String,
email : String,
name : String
},
apiKey: String,
stations : [stationSchema]
},
{
usePushEach: true
}
);
Api handler
app.get('/api/stations/:stationName/measures', function(req, res, next) {
var user = {
apiKey: req.user.apiKey
}
const query = {
apiKey: user.apiKey,
stations.stationName': req.params.stationName
}
const options = {
'stations.measures': 1
}
User.findOne(query, options)
.exec()
.then(stations => {
res.status(200).send(stations)
})
.catch(err => {
console.log(err);
res.status(400).send(err);
})
});
There are two stations under one user:
[
{
"_id": "5c39c99356bbf002fb092ce9",
"stations": [
{
"stationName": "livingroom",
"mac": "5C:CF:7F:77:12:FB",
"_id": "5c39c9ab56bbf002fb092cea",
"lastUpdated": "2019-01-12T11:07:01.802Z",
"syncReadings": false,
"measures": [],
"humidity": [],
"temperature": [
{
"date": "2019-01-12T11:07:01.802Z",
"temperature": "20"
}
]
},
{
"stationName": "office",
"mac": "5C:CF:7F:77:12:FC",
"_id": "5c39cacdce4ac903123f0150",
"measures": [],
"humidity": [],
"temperature": []
}
]
}
]
API call
http://localhost:8080/api/stations/livingroom/measures
Result
{
"_id": "5c39c99356bbf002fb092ce9",
"stations": [
{
"measures": []
},
{
"measures": []
}
]
}
Projection options tried
const options = {
'stations.measures': 1
}
const options = {
'stations.$.measures': 1
}
const options = {
'stations.$': 1,
'stations.$.measures': 1
}
const options = {
'stations.$': 1,
'stations.measures': 1
}
What am I doing wrong?

Answer 1

try using these querying params only and after that you will get a user with a requested station..
var user = {
apiKey: req.user.apiKey
}
const query = {
apiKey: user.apiKey,
'stations.stationName': req.params.stationName
}
then do this
User.findOne(query, options)
.exec()
.then(stations => {
for(let station of stations){
if(station.measures[1]){ // here it is the index
res.status(200).send(stations);
}
}
})
.catch(err => {
console.log(err);
res.status(400).send(err);
})
actually in mongoose you cannot query sub-sub documents to you will have to you this approach.. You can only query sub docs only like you have done