gistfile1.txt

use geospatial
elng=-45.929887
slat=-2.940540
nlat=73.844279
wlng=-143.255854

wsize = (wlng < elng) ? elng-wlng : (180-wlng)+(180-Math.absw(elng))
hsize = nlat-slat
csize = (wsize > hsize) ? wsize/3 : hsize/3


db.dispensers.find({"loc": {$within: {$box: [[wlng,slat], [elng,nlat]]}},
                                  "product_id": 41,
                                  "business_type": {$in: [1,2] }})

map = function() {
    vindex = Math.floor((this.loc.x+90)/csize)
    hindex = Math.floor((this.loc.y+180)/csize)
    key    = hindex + ":" + vindex
    emit(key, this.id)
}

reduce = function(key, ids) {
  result = {a:[]}
  ids.forEach(function(id) {
    if(result.a.size < 10) {
      result.a.push(id)
    }
  })
  return result;
}

db.dispensers.mapReduce(map,
                        reduce,
                        {
                          "out": {"inline": 1},
                          "scope": {"csize": csize},
                          "query": {"loc": {$within: {$box: [[wlng,slat], [elng,nlat]]}},
                                  "product_id": 41,
                                  "business_type": {$in: [1,2] }}
                        })