$ geowithin:$ polygon不使用2dsphere索引 [英] $geowithin:$polygon doesn't use 2dsphere index

问题描述

我正在收集如下文件:

{
    "_id" : ObjectId("5bc15f23d672e9086ca4fbac"),
    "Location" : {
        "GeoJson" : {
            "type" : "Point",
            "coordinates" : [14.4199254356, 50.0700249768]
        }
}

我已经按照以下步骤创建了索引

And I have Index created as following

{ Location.GeoJson2dsphere : "2dsphere" }

现在当我使用$polygon进行搜索时出现了问题，我得到了结果，但是查询未使用索引，因此速度很慢.这是查询

And now to the problem when I use the $polygon for searching, i've got the results, but query is not using index, so it's slow. Here is the query

.find({"Location.GeoJson" : {
      "$geoWithin" : {
      "$polygon" : [ 
        [14.4182910543168, 50.0891393887804], 
        [14.4491901021683, 50.0891393887804], 
        [14.4491901021683, 50.0671069088523], 
        [14.4182910543168, 50.0671069088523]
      ]
    }
  }
})

但是当我改用$ Geometry时，它使用的是索引.

But when I use $Geometry instead, it is using index.

.find({"Location.GeoJson" : {
  "$geoWithin" : 
    {"$geometry" :
      {"type" : "Polygon",
        "coordinates" : [[ 
          [14.4182910543168, 50.0891393887804], 
          [14.4491901021683, 50.0891393887804], 
          [14.4491901021683, 50.0671069088523], 
          [14.4182910543168, 50.0671069088523],
          [14.4182910543168, 50.0891393887804]
        ]]
      }}
    }})

是否有任何原因导致第一个查询不使用索引? Mongo手册对此没有说什么. 您能指出我，使用$ polygon搜索索引该怎么做，还是我需要重写我应用程序中的所有查询才能使用$ geometry.我正在使用C#驱动程序，其语法如下所示:

Is there any reason why the first query isn't using the index? Mongo manual is not saying anything about this. Can you point me, what to do to use $polygon for searching index, or do I need to rewrite all the queries in my app, to use $geometry. I am using C# driver where the syntax looks like this:

Builders<Offer>.Filter.GeoWithinPolygon(a => a.Location.GeoJson, polygon);

但是，这将产生第一个不使用索引的查询.

However, this is producingf the first query, which is not using index.

推荐答案

我不为mongo工作，所以不会冒险猜测为什么(除了旧数据模型还是新数据模型)令新手感到困惑，但这是如何 mongo如何区分 infinite-flat-2d ($多边形查询)索引和 spherical 索引($ geometry查询)

I don't work for mongo, so won't hazard a guess as to why (beyond legacy vs new data models) being confusing for newcomers, but here is how mongo differentiates between an infinite-flat-2d ($polygon query) index and a spherical index ($geometry query)

传递 $ polygon 会针对旧版2d索引，而 $ geometry 会针对2d球形索引. Mongo将这些查询分为两种不同的对象类型

passing a $polygon targets a legacy 2d index, where or a $geometry targets the 2d-spherical index. Mongo splits out these queries to two different object types

此处: https ://github.com/mongodb/mongo/blob/master/src/mongo/db/geo/geoparser.cpp#L785-L790

Mongo确实说只能通过 $ geometry 查询(不是传统的 $ polygon 查询)只能访问2dsphere索引

Mongo does say that the 2dsphere index is only accessable though a $geometry query (not the legacy $polygon query)

此处: https://docs.mongodb.com/手册/教程/query-a-2dsphere-index/

如您所述: Mongo超级有帮助，即使您的查询不匹配，它仍然可以返回数据.

As you noted: Mongo is super helpful in that it can still return data, even if you've mismatched your queries.

为什么 $ polygon 甚至不再是东西?

Why is $polygon even a thing anymore?

对于那些希望在无限的平面上使用2d索引的人，Mongo继续支持非球面2d索引.也许是用于视频游戏，或者用于无限平坦的平面足以避免浮点数学运算(以及相关的舍入问题)的任何用途

Mongo continues to support non-spherical 2d indexes for those that want a 2d index on an infinite flat surface. Perhaps for video games or for any use where an infinite flat surface is a good enough approximation to avoid floating point math (and associated rounding questions)

在此处描述: https://docs.mongodb.com /manual/tutorial/query-a-2d-index/

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