$polygon¶

Definition定义¶

$polygon¶

Specifies a polygon for a geospatial $geoWithin query on legacy coordinate pairs. 为旧坐标对上的地理空间$geoWithin查询指定多边形。The query returns pairs that are within the bounds of the polygon. 查询返回多边形边界内的对。The operator does not query for GeoJSON objects.运算符不查询GeoJSON对象。

To define the polygon, specify an array of coordinate points:要定义多边形，请指定坐标点数组：

{
   <location field>: {
      $geoWithin: {
         $polygon: [ [ <x1> , <y1> ], [ <x2> , <y2> ], [ <x3> , <y3> ], ... ]
      }
   }
}

The last point is always implicitly connected to the first. 最后一点始终隐式连接到第一点。You can specify as many points, i.e. sides, as you like.您可以根据需要指定任意多个点（即边）。

Important

If you use longitude and latitude, specify longitude first.如果使用经度和纬度，请先指定经度。

Behavior行为¶

The $polygon operator calculates distances using flat (planar) geometry.$polygon运算符使用平面几何体计算距离。

Applications can use $polygon without having a geospatial index. 应用程序可以使用$polygon，而无需地理空间索引。However, geospatial indexes support much faster queries than the unindexed equivalents.然而，地理空间索引支持的查询速度要比未索引的索引快得多。

Only the 2d geospatial index supports the $polygon operator.只有2d地理空间索引支持$polygon运算符。

Example示例¶

The following query returns all documents that have coordinates that exist within the polygon defined by [ 0 , 0 ], [ 3 , 6 ], and [ 6 , 0 ]:以下查询返回所有文档，这些文档的坐标存在于由[ 0 , 0 ]、[ 3 , 6 ]和[ 6 , 0 ]定义的多边形内：

db.places.find(
  {
     loc: {
       $geoWithin: { $polygon: [ [ 0 , 0 ], [ 3 , 6 ], [ 6 , 0 ] ] }
     }
  }
)