从 MongoDB 获取唯一的 GEO 数据

Question

我的 Mongo 数据库中有以下 GEO 数据。

db.car.ensureIndex({"loc":"2d" , "name" :1})

db.car.save({ "name":"Toyota car", "affiliation":"Toyota", "loc":{"lon":55.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Honda car", "affiliation":"Honda", "loc":{"lon":58.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Skoda", "affiliation":"Skoda", "loc":{"lon":52.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Ford", "affiliation":"Ford", "loc":{"lon":45.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Audi SUV", "affiliation":"Audi", "loc":{"lon":35.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Benz", "affiliation":"Benz", "loc":{"lon":75.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Skoda", "affiliation":"Skoda", "loc":{"lon":50.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Benz", "affiliation":"Skoda", "loc":{"lon":51.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Skoda SUV", "affiliation":"Skoda", "loc":{"lon":50.93939251390387,"lat":-113.999}})
    db.car.save({"name":"Honda", "affiliation":"Skoda", "loc":{"lon":55.93939251390387,"lat":-113.999}})

我正在尝试为给定的收音机获取最接近的“名称”。

当我运行以下查询时

db.car.find({"loc" : {"$within" : {"$center" : [[50.93939251390,-114],5]}}})

我明白了

enter code here

> db.car.find({"loc" : {"$within" : {"$center" : [[50.93939251390,-114],5]}}})
{ "_id" : ObjectId("501cc07eebb626e104d5a23b"), "name" : "Skoda", "affiliation" : "Skoda", "loc" : { "lon" : 50.93939251390387, "lat" : -113.999 } }
{ "_id" : ObjectId("501cc07eebb626e104d5a237"), "name" : "Skoda", "affiliation" : "Skoda", "loc" : { "lon" : 52.93939251390387, "lat" : -113.999 } }
{ "_id" : ObjectId("501cc07eebb626e104d5a23c"), "name" : "Benz", "affiliation" : "Skoda", "loc" : { "lon" : 51.93939251390387, "lat" : -113.999 } }
{ "_id" : ObjectId("501cc07febb626e104d5a23d"), "name" : "Skoda SUV", "affiliation" : "Skoda", "loc" : { "lon" : 50.93939251390387, "lat" : -113.999 } }

但我想检索半径中的唯一“名称”，如下所示。

> db.car.find({"loc" : {"$within" : {"$center" : [[50.93939251390,-114],5]}}})
{ "_id" : ObjectId("501cc07eebb626e104d5a23b"), "name" : "Skoda", "affiliation" : "Skoda", "loc" : { "lon" : 50.93939251390387, "lat" : -113.999 } }
{ "_id" : ObjectId("501cc07eebb626e104d5a23c"), "name" : "Benz", "affiliation" : "Skoda", "loc" : { "lon" : 51.93939251390387, "lat" : -113.999 } }
{ "_id" : ObjectId("501cc07febb626e104d5a23d"), "name" : "Skoda SUV", "affiliation" : "Skoda", "loc" : { "lon" : 50.93939251390387, "lat" : -113.999 } }

如何在其中添加约束？

Answer 1

您无法将这种分组约束添加到您的查询中（至少对于 MongoDB 2.0.x），因此您必须在应用代码中迭代结果以提取您需要的内容。

假设以下创建了一个示例：

• 跟踪给定名称的匹配数会很有用
• 您只想包含给定名称的最接近匹配项的详细信息
• MongoDB geoNear() 按距离排序，因此第一个匹配项应该是最近的

这是使用 JS shell：

// Hash to save results
> var cars = {}

// Find closest cars to given geo point using geoNear
>   db.runCommand(
        { geoNear: 'car', near : [50.93939251390,-114], num:5}
    ).results.forEach(
        function(doc) {
            if (cars[doc.obj.name]) {
                // Increment number of matches for this name
                cars[doc.obj.name]['matches'] = cars[doc.obj.name]['matches'] + 1;
            } else {
                // Closest match found
                doc.obj['matches'] = 1;
                doc.obj['distance'] = doc.dis;
                cars[doc.obj.name] = doc.obj;
            }
        }
    )

// Check the results
> cars
{
    "Skoda" : {
        "_id" : ObjectId("501d108c9d2b5b2b5443712d"),
        "name" : "Skoda",
        "affiliation" : "Skoda",
        "loc" : {
            "lon" : 50.93939251390387,
            "lat" : -113.999
        },
        "matches" : 2,
        "distance" : 0.0010000000000047748
    },
    "Skoda SUV" : {
        "_id" : ObjectId("501d108c9d2b5b2b5443712f"),
        "name" : "Skoda SUV",
        "affiliation" : "Skoda",
        "loc" : {
            "lon" : 50.93939251390387,
            "lat" : -113.999
        },
        "matches" : 1,
        "distance" : 0.0010000000000047748
    },
    "Benz" : {
        "_id" : ObjectId("501d108c9d2b5b2b5443712e"),
        "name" : "Benz",
        "affiliation" : "Skoda",
        "loc" : {
            "lon" : 51.93939251390387,
            "lat" : -113.999
        },
        "matches" : 1,
        "distance" : 1.0000005000037404
    },
    "Ford" : {
        "_id" : ObjectId("501d108c9d2b5b2b5443712a"),
        "name" : "Ford",
        "affiliation" : "Ford",
        "loc" : {
            "lon" : 45.93939251390387,
            "lat" : -113.999
        },
        "matches" : 1,
        "distance" : 5.000000099996134
    }
}

此类搜索结果的一种常见方法是显示在列表中找到的所有匹配项，并将它们绘制在地图上。 理想情况下，您的地图视图将支持某种Marker Clustering，以根据用户选择的缩放级别自动对标记进行分组。