Khudoyshukur Juraev [11:50 AM] Hi, all! I am usi...

# server

[Khudoyshukur Juraev]

Khudoyshukur Juraev [11:50 AM]
Hi, all!

I am using ktor in the backend side.
I have tables:

Drivers {
id: Long
......
}

DriverLocations {
id: Long
driverId: Long
latitude: Double
longitude: Double
datetime: Long
}

I need to query the drivers within 1 km radius from Some point.
To calculate distance, i can use:

fun haversine(lat1: Double, lon1: Double, lat2: Double, lon2: Double): Double {
    val earthRadius = 6371000 // Radius of the earth in meters

    val latDistance = Math.toRadians(lat2 - lat1)
    val lonDistance = Math.toRadians(lon2 - lon1)
    val a = sin(latDistance / 2) * sin(latDistance / 2) +
            cos(Math.toRadians(lat1)) * cos(Math.toRadians(lat2)) *
            sin(lonDistance / 2) * sin(lonDistance / 2)
    val c = 2 * atan2(sqrt(a), sqrt(1 - a))

    return earthRadius * c // Calculate the distance in meters
}

However, i do not now how to query this with exposed?

[hfhbd]

I would write plain sql code first, then transform this sql code to exposed dsl. Maybe you need to create some functions.

[Christopher Hübner]

@Khudoyshukur Juraev My approach:

1. Set up a database and query with plain sql.
2. Create Test-Cases for the kotlin-query.
3. Convert the sql to exposed dsl. I am not sure as well how to convert, but as a developer it is your job to make the research needed.
4. Test you solution.
Good luck 🙂

[Khudoyshukur Juraev]

@hfhbd @Christopher Hübner
Thank you guys. Figured out the solution with your suggestions.