尝试使用mongodb的filter.near
尝试使用mongodb的filter.near
提问于 2019-06-03 08:15:33
我试图从嵌套的mongodb文档中找到最接近的cordinations。我一直得到的错误如下：
我已经尝试了我能想到的一切。我试图添加索引2d，但两者都不起作用。
var point = GeoJson.Point(GeoJson.Geographic(38.8086, -85.1792));
var locationQuery = new FilterDefinitionBuilder<Book>().NearSphere(tag => tag.CitiesInBook[-1].Location, point,
5000);
var query = collection.Find(locationQuery).Limit(10);
var a = query.ToList();
Planner返回错误
无法找到$ geoNear查询的索引。
回答 1
Stack Overflow用户
发布于 2019-06-03 17:25:29
这是使用MongoDB.Entities的解决方案。我使用了标签和城市之间的一对多关系，而不是将城市嵌入标签实体中。
using MongoDB.Entities;
using MongoDB.Driver.GeoJsonObjectModel;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using System.Linq;
namespace StackOverflow
{
public class Program
{
public class Tag : Entity
{
public string Name { get; set; }
public Many<City> Cities { get; set; }
public Tag() => this.InitOneToMany(() => Cities);
}
public class City : Entity
{
public string Name { get; set; }
public GeoJsonPoint<GeoJson2DGeographicCoordinates> Location { get; set; }
}
static void Main(string[] args)
{
new DB("test");
//create an index
DB.Index<City>()
.Key(c => c.Location, KeyType.Geo2DSphere)
.Option(o => o.Background = false)
.Create();
var paris = new City
{
Name = "paris",
Location = GeoJson.Point(new GeoJson2DGeographicCoordinates(48.8539241, 2.2913515))
};
paris.Save();
var versailles = new City
{
Name = "versailles",
Location = GeoJson.Point(new GeoJson2DGeographicCoordinates(48.796964, 2.137456))
};
versailles.Save();
var poissy = new City
{
Name = "poissy",
Location = GeoJson.Point(new GeoJson2DGeographicCoordinates(48.928860, 2.046889))
};
poissy.Save();
var scifi = new Tag { Name = "sci-fi" };
scifi.Save();
scifi.Cities.Add(paris);
scifi.Cities.Add(versailles);
scifi.Cities.Add(poissy);
var horror = new Tag { Name = "horror" };
horror.Save();
horror.Cities.Add(poissy);
var eiffelTower = GeoJson.Point(GeoJson.Geographic(48.857908, 2.295243));
//find matching city IDs within 20kms of eiffel tower.
var cities = DB.Find<City, string>()
.Match(f => f.NearSphere(c => c.Location, eiffelTower, 20000))
.Project(c => c.ID)
.Execute();
//select only the joins for matching city IDs
var joins = from j in scifi.Cities.JoinQueryable()
where cities.Contains(j.ChildID)
select j;
//get the matching tags from previous step's joins
var tags = from j in joins
join t in DB.Queryable<Tag>() on j.ParentID equals t.ID
select t ;
//result is scifi because horror is too far from paris
var result = tags.Distinct().ToArray();
}
}
}
上述程序向mongodb发出2个查询，如下所示
第一个查询：
{
"find": "City",
"filter": {
"Location": {
"$nearSphere": {
"$geometry": {
"type": "Point",
"coordinates": [
48.857908,
2.295243
]
},
"$maxDistance": 20000
}
}
},
"projection": {
"_id": NumberInt("1")
}
第二个查询：
{
"$match": {
"ChildID": {
"$in": [
ObjectId("5cf3fc1f4090311b6415b75d"),
ObjectId("5cf3fc1f4090311b6415b75e")
]
}
}
}, {
"$lookup": {
"from": "Tag",
"localField": "ParentID",
"foreignField": "_id",
"as": "t"
}
}, {
"$unwind": "$t"
}, {
"$group": {
"_id": "$t"
}
}
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100006902
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