mongodb, sorting by geoNear and date?

Question

how to sort by proximity and date in mongoDB? I tried this. But they just sort by date:

   coll.find({'date':{$gte:date},'location':{$nearSphere:[lat,lng]}}).sort({'date':1}).execFind(function (err, docs) {})

I appreciate the help.

Answer 1

There's no direct way to use $near or $nearSphere and sort by another field, because both of these operators already sort the results of doing a find(). When you sort again by 'date', you're re-sorting the results. What you can do, however, is grab results from the $nearSphere incrementally, and sort each set of results. For example:

function sortByDate(a, b) { return a.date - b.date; }

// how many results to grab at a time
var itersize = 10;
// this will hold your final, two-way sorted results
var sorted_results = new Array();
for (var i=0, last=db.coll.count(); i<last-itersize; i+=itersize) {
    var results = db.coll.find( {"date":{$gte:date},
                                 // longitude, then latitude
                                 "location":[lng, lat]} ).skip(i).limit(itersize).toArray();
    // do date sorting app-side for each group of nearSphere-sorted results
    sorted_results = sorted_results.concat( results.sort(sortByDate) );
}

You should also be aware of the order you specify geospatial coordinates in mongodb queries. MongoDB uses the geojson spec, which does coordinates in X, Y, Z order (i.e., longitude, latitude).