GeoFire Query Gives Only Own Location

[SamaritanMachine]

Using GeoFire 3.0 and Swift 4

The problem is when I query locations with given radius, it gives only one location and the location is own location. When I run the app from simulator and it gives only one location again and this location is simulator's location. I can't get any other users' locations.

I want to get all location entries in database according to given radius.

Here is my setLocation func:

     self.geoFire.setLocation(location, forKey: uid) { (error) in
          }

And this is my query:

self.geoFire.query(at: self.userLocation!, withRadius: 2.0).observe(.keyEntered) { (str, loc) in

            print("*****", str, loc.coordinate.longitude, loc.coordinate.latitude)

        }

I'm truly sure that all these locations are in given radius.

Also, I'm giving this tip on console.

Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding ".indexOn": "g" at /Users/6VRAyf3HFZfFXUH5TWBtB6v1om22 to your security rules for better performance

What does it mean?