使用 geonear 的 Mongoose 聚合

Question

我正在尝试使用 Mongoose geoNear 命令实现分页。 geoNear 似乎不支持跳过，我知道聚合会起作用（分页会带来性能成本）。如何将其转换为聚合查询以跳过多个文档？

exports.near = function(req, res) {
    if(req.query.lat && req.query.lng) {
        var point = {
            type: "Point", coordinates : [Number(req.query.lng), Number(req.query.lat)]
        };
        var queryParams = {
            spherical: true,
            skip: 0,
            limit: 10,
            distanceMultiplier: 6371 // radians to kilometers. (The radius of the Earth is approximately 3,959 miles or 6,371 kilometers.)
        };
        if(req.query.q) {
            var matcher = new RegExp(req.query.q, "i");
            queryParams.query = {
                $or: [
                    {'name': matcher },
                    {'address.full': matcher}
                ]
            };
        }
        if(req.query.limit) {
            queryParams.limit = parseInt(req.query.limit, 10);
        }
        if(req.query.offset) {
            queryParams.skip = parseInt(req.query.offset, 10);
        }
        Venue.geoNear(point, queryParams, function(error, results, stats) {
            // TODO
        });
    }
};

Answer 1

location.aggregate({"$geoNear": { "near": { "type": "Point", "coordinates": [parseFloat(req.params.lon), parseFloat(req.params.lat)] }, "maxDistance":500, 'distanceField' : 'distance', spherical: true
      }}, 
    function(err, places) {
   if(!err){
           console.log(places);
            res.send('({"records":' + JSON.stringify(places) + '});');
        }
        else{
            console.log(err);
            res.send("error coming")
        }
    });`

Above Query working fine in mongo shell but not working in mongoose 

Answer 2

您可以为此使用聚合框架，并且没有真正的惩罚，因为操作本质上是相同的。

但是，虽然目前 mongoose .find() 方法与等效的 $nearSphere 运算符存在问题，但您始终可以获取原始节点驱动程序连接对象并进行查询。

如果您准备实施一点处理，您甚至不需要丢弃诸如“人口”之类的东西。

这是我的测试数据：

{ 
    "_id" : "P1",
    "amenity" : "restaurant", 
    "shape" : { 
        "type" : "Point", 
        "coordinates" : [ 2, 2 ] 
    }
}
{ 
    "_id" : "P3",
    "amenity" : "police",
    "shape" : { 
        "type" : "Point", 
        "coordinates" : [ 4, 2 ]
    }
}
{ 
    "_id" : "P4",
    "amenity" : "police",
    "shape" : {
        "type" : "Point",
        "coordinates" : [ 4, 4 ]
    }
}
{ 
    "_id" : "P2",
    "amenity" : "restaurant",
    "shape" : { 
        "type" : "Point",
        "coordinates" : [ 2, 4 ]
    }, 
    "info" : ObjectId("539b90543249ff8d18e863fb")
}

以及处理这个的基本代码：

var mongoose = require('mongoose'),
    async = require('async'),
    Schema = mongoose.Schema;


mongoose.connect('mongodb://localhost');

var infoSchema = new Schema({
  "description": String
});

var shapeSchema = new Schema({
  "_id": String,
  "amenity": String,
  "shape": {
    "type": { "type": String },
    "coordinates": []
  },
  "info": { "type": Schema.Types.ObjectId, "ref": "Info" }
});

var Shape = mongoose.model( "Shape", shapeSchema );
var Info = mongoose.model( "Info", infoSchema );


Shape.collection.find(
  {
    "shape": {
      "$nearSphere": {
        "$geometry": {
          "type": "Point",
          "coordinates": [ 2, 4 ]
        }
      }
    }
  },
  {
    "skip": 0, "limit": 2
  },
  function(err,cursor) {

    cursor.toArray(function(err,shapes) {

      Shape.populate( shapes, { path: "info" }, function(err,docs) {
        if (err) throw err;

        console.log( JSON.stringify( docs, undefined, 4 ) );
      });

    });

  }
);

所以你在光标上使用了 skip 和 limit 操作，返回了一个光标，甚至将文档处理回“Mongoose Documents”，所以你可以在它们上面调用.populate()之类的函数。

我希望$nearSphere 的当前问题能够很快得到解决。

或者使用聚合代替：

Shape.aggregate(
  [
    { "$geoNear": {
        "near": {
          "type": "Point",
          "coordinates": [ 2, 4 ]
        },
        "spherical": true,
        "distanceField": "dis"
    }},
    { "$skip": 0 },
    { "$limit": 2 }

  ],
  function(err,shapes) {
    if (err) throw err;
    //console.log( shapes );

    shapes = shapes.map(function(x) {
      delete x.dis;
      return new Shape( x );
    });

    Shape.populate( shapes, { path: "info" }, function(err,docs) {
      if (err) throw err;

      console.log( JSON.stringify( docs, undefined, 4 ) );
    });

  }
);

您可以在其中执行相同的操作，例如使用 .populate()。两种情况都返回与“填充”字段匹配的结果：

{
    "_id": "P2",
    "amenity": "restaurant",
    "info": {
        "_id": "539b90543249ff8d18e863fb",
        "description": "Jamies Restaurant",
        "__v": 0
    },
    "shape": {
        "type": "Point",
        "coordinates": [
            2,
            4
        ]
    }
},
{
    "info": null,
    "_id": "P4",
    "amenity": "police",
    "shape": {
        "type": "Point",
        "coordinates": [
            4,
            4
        ]
    }
}

当然，如果您不需要球面几何计算，那么 $near 运算符与 .find() 的 Mongoose 实现完美配合