Need to calculate length in km of line in RethinkDB - rethinkdb

Question

I have a Line object in a document inside RethinkDB
I am looking for an easy/efficient way of calculating the real world distance of the line.
My initial strategy was to pull the line out of the database and calculate it inside Node.js but ideally would like a way to do this 'in the box'
I cannot find a way to iterate over the coordinates of the line inside ReQl and use the distance function to calculate.
Any help is greatly appreciated.

Answer 1

Unfortunately, the only way I could find how to do this, as it seems that the points within the r.line object are inaccessible, is to convert the line into GeoJSON, convert to points, and then return the calculation.
Using an object like this:
{
id: 101,
route: r.line([-122.423246,37.779388], [-121.886420,37.329898])
}
Your query would look like this:
r.table('data').get(101)('route').do(function(doc){
var points = doc.toGeojson()("coordinates").map(function(point){
return r.point(point(0), point(1));
});
return {
"distance": points(0).distance(points(1))
}
});
Or, as you probably have a whole bunch of line distances to calculate:
r.table('data').hasFields("route")('route').map(function(doc){
var points = doc.toGeojson()("coordinates").map(function(point){
return r.point(point(0), point(1));
});
return {
line: points(0).distance(points(1))
}
});
I've also submitted a Github issue to see if we can find an improvement!