Least data-heavy way to retrieve 5 closest users in Firebase/Swift? - ios

Question

Let's imagine I have a Firebase setup like this, except with 10,000 users:
"users" : {
"user 1" : {
"latitude": 1234567,
"Longitude": 7654321,
"name": "Name 1"
},
"user 2" : {
"latitude": 1234567,
"longitude": 7654321,
"name": "Name 2"
},
"user 3" : {
"latitude": 1234567,
"Longitude": 7654321,
"name": "Name 3"
},
"user 4" : {
"latitude": 1234567,
"Longitude": 7654321,
"name": "Name 4"
},
}
What would be the least data-intensive way to generate a list of the 5 users closest to me? Very new to this, so the only solutions I can think of would require querying all 10,000 users.

Answer 1

I am very new to this subject, therefore I can only point you in the right direction. Essentially the way you're storing user location is not optimal. The best way to do it is to use GeoFire a newish addition to the Firebase service. How it works is you should have a large location object and you store the geolocation of those users using that users key. Here's an example.
{
Locations: {
-KH35xPkJmX0UTSG8DuM : {
"g" : "randomID",
"l" : {
"0" : "latitude",
"1" : "longitude"
}
}
}
}
{
Users: {
-KH35xPkJmX0UTSG8DuM : {
"username" : "Joe Sloan"
}
}
}
Your locations object will have 10,000 users keys and geoLocations. the value of "g" and "l" object are set when you use
geoFire.setLocation(CLLocation(latitude: 37.7853889, longitude: -122.4056973), forKey: "firebase-hq")
Google has optimized the query for users within a similar location.
let center = CLLocation(latitude: 37.7832889, longitude: -122.4056973)
// Query locations at [37.7832889, -122.4056973] with a radius of 600 meters
var circleQuery = geoFire.queryAtLocation(center, withRadius: 0.6)
The circleQuery variable should contain a Firebase dictionary of the closest users. As I said I haven't had a chance to really delve deeper but this should give you a start.