如何在地理空间搜索中返回与MongoDB和Mongoose的距离？

Question

我使用Mongoose 3.5.3和Node.js 0.8.8，我很惊讶地发现距离给定点的距离没有返回到结果中。是否有可能允许返回距离？它必须拥有它，因为我的结果似乎按照预期的距离排序。

exports.nearBuilding = function (req, res, next) { 
    var area = { 
     center: [parseFloat(req.params.longitude), parseFloat(req.params.latitude)], 
     radius: parseFloat(req.params.distance)/3963.192 }; 

    var query = Building.find().where('coords').within.centerSphere(area); 

    query.exec(function (error, docs) { 
     var records = {'records': docs}; 
     if (error) { 
      process.stderr.write(error); 
      res.send(error, 500); 
     } 
     if (req.params.callback !== null) { 
      res.contentType = 'application/javascript'; 
     } 
     res.send(records); 
     return next(); 
    }); 
}; 

Answer 1

可以使用geoNear函数返回距离：

Building.collection.geoNear(longitude, latitude, {maxDistance: radius }, cb); 

这里有API选项：

/** 
* Execute the geoNear command to search for items in the collection 
* 
* Options 
* - **num** {Number}, max number of results to return. 
* - **maxDistance** {Number}, include results up to maxDistance from the point. 
* - **distanceMultiplier** {Number}, include a value to multiply the distances with allowing for range conversions. 
* - **query** {Object}, filter the results by a query. 
* - **spherical** {Boolean, default:false}, perform query using a spherical model. 
* - **uniqueDocs** {Boolean, default:false}, the closest location in a document to the center of the search region will always be returned MongoDB > 2.X. 
* - **includeLocs** {Boolean, default:false}, include the location data fields in the top level of the results MongoDB > 2.X. 
* - **readPreference** {String}, the preferred read preference ((Server.PRIMARY, Server.PRIMARY_PREFERRED, Server.SECONDARY, Server.SECONDARY_PREFERRED, Server.NEAREST). 
* 
* @param {Number} x point to search on the x axis, ensure the indexes are ordered in the same order. 
* @param {Number} y point to search on the y axis, ensure the indexes are ordered in the same order. 
* @param {Objects} [options] options for the map reduce job. 
* @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from the geoNear method or null if an error occured. 
* @return {null} 
* @api public 

在你的情况，你会做这样的事情：

 exports.nearBuilding = function (req, res, next) { 

     var query = Building.collection.geoNear(parseFloat(req.params.longitude), parseFloat(req.params.latitude), { distance: parseFloat(req.params.distance)/3963.192}, function (error, docs) { 

      if (error) { 
       process.stderr.write(error); 
       res.send(error, 500); 
      } 
      if (req.params.callback !== null) { 
       res.contentType = 'application/javascript'; 
      } 
      // Docs are turned as an array of objects that contain distance (dis) and the object (obj). 
      // Let's concatenate that into something cleaner - i.e. the distance as part of object 

      var results = [] 
      docs.forEach(function(doc) { 
       doc.obj.distance = doc.dis; 
       results.push(doc.obj); 
      }); 
      var records = {'records': results};  

      res.send(records); 
      return next(); 
     }); 
    }; 

Answer 2

当前（3 0.8）猫鼬的构建提供了一个Model方法geoNear为此目的：

Building.geoNear(
    [long, lat], 
    { maxDistance: 300, spherical: true }, 
    function(err, results, stats) { 
     // results is an array of result objects like: 
     // {dis: distance, obj: doc} 
    } 
); 

Answer 3

如果使用2dsphere坐标（你应该）代码应如下。距离d以米为单位。

var point = { coordinates: [lng, lat], type: 'Point' };   
 

 
Entity.geoNear(point, {maxDistance: d, spherical: true}, function(err, docs) { 
 
    if (err) { return next(err); } 
 

 
    var entities = []; 
 

 
    docs.forEach(function(doc) { 
 
    doc.obj.distance = doc.dis; 
 
    entities.push(doc.obj); 
 
    }); 
 

 
    res.json(entities); 
 
});