如何修复MongooseJS排序和跳过

Question

I'm working on an Express API using mongoose for MongoDB. In the code below I'm trying to find GeoJson objects that are within a certain distance, Sort them so that the newest objects appear first, skip to a certain document before returning the specified number of objects in the "limit".

// Find all of the stacks in a given radius
router.param("range", function(req, res, next, range) {
  if(range === "1") {
    var radius = 8125; // Meters. (5 Miles)
  } else if(range === "0") {
    var radius = 45.75; // Meters. (150 Feet)
  }

  var skipTo = parseInt(req.params.skip);
  var origin = [parseFloat(req.params.lon), parseFloat(req.params.lat)]; // [longitude, latitude]
  var userLocation = { type: "Point", coordinates: origin };
  var options = { maxDistance: radius,
                  spherical : true,
                  sort: {
                     createdAt: -1 // Sort by Date Added DESC
                  },
                  skip: skipTo, // Skip to a specific point
                  limit: 15 // How many returned
                 };

  Stack.geoNear(userLocation, options, function(err, result, stats) {
    if(err) return next(err);

    if(!result) {
      err = new Error("Not Found");
      err.status = 404;
      return next(err);
    }

    req.locals = result;
    next();
  });
});

When I run the code the geoNear() function works perfectly as does the limit function. My issues are with sort and skip. It is almost as if sort and skip are ignored. I have looked at the mongo and mongoose docs as well as similar code online and I can't find a fix anywhere. How can I make it so that when I try to get the documents in a certain area my results are properly skipped over and organized by date?

Answer 1

Can you try changing this:

Stack.geoNear(userLocation, options, function(err, result, stats) {

to the following:

var options = { maxDistance: radius, spherical : true };

Stack.geoNear(userLocation, options)
    .sort({CreatedAt: -1})
    .skip(skipTo)
    .limit(15)
    .exec(function(err, result, stats) {

I think sort, skip, and limit need to be called directly and not specified in the options.

Answer 2

I fixed the issue yesterday. The code is posted below.

// Find all of the stacks in a given radius
router.param("range", function(req, res, next, range) {

if(range === "1") {
    var radius = 8125; // Meters. (5 Miles)
  } else if(range === "0") {
    var radius = 45.75; // Meters. (150 Feet)
  }

  var skipTo = parseInt(req.params.skip);
  var origin = [parseFloat(req.params.lon), parseFloat(req.params.lat)]; // [longitude, latitude]
  var userLocation = { type: "Point", coordinates: origin };
  var options = { maxDistance: radius,
                  spherical: true,
                  limit: 15 // How many returned
                };

  // Query database for Stack Objects
  Stack.aggregate([
    { '$geoNear': {
        'near': userLocation, // The point where the user is located
        'distanceField': 'dist.calculated', // The distance the Stack Object is from the user
        'maxDistance': radius, // The furthest distance a Stack Object can be from the user
        'spherical': true
      }
    },
    { '$sort': { 'createdAt': -1 } }, // Return newest Stack Object first
    { '$skip': skipTo }, // Paginate
    { '$limit': 15 } // Number of Stacks returned
  ]).exec(function(err, result, stats) {
    if(err) return next(err);

    if(!result) {
      err = new Error("No Stacks Found");
      err.status = 404;
      return next(err);
    }

    req.locals = result;
    next();
  });
});