MoNGODB空间数据库操作常用函数

 

一、数据类型定义

1. 在mongodb中,空间数据以geojson和坐标对的形式保存
2. Geojson数据中有两个field组成，一个是type 用来定义geojson对象类型，一个是坐标对用来定义
3. 经度需在[-180,180],纬度需在[-90,90]之间
4. Type定义：<field>: { type: <GeoJSON type> , coordinates: <coordinates> }

location: {

      type: "Point",

      coordinates: [-73.856077, 40.848447]

}

1. 坐标对定义：（1）通过数组<field>: [<longitude>, <latitude> ]（2）嵌入文档<field>: { <field1>: <longitude>, <field2>: <latitude> }

二、地理查询

1．建立空间索引 2dsphere：db.collection.createIndex( { <location field> : "2dsphere" } ) 此处的location field 可以使geojson或者是坐标对

2.空间索引不能用于碎片关键词

3.sharded collections碎片集合查询时，$near和$nearSpher不能使用，可以用geoNear和$geoNear代替

4.

Operation	Spherical/Flat Query	Notes
$near (GeoJSON centroid point in this line and the following line, 2dsphere index)	Spherical	See also the $nearSphere operator, which provides the same functionality when used with GeoJSON and a 2dsphere index.
$near (legacy coordinates, 2d index)	Flat
$nearSphere (GeoJSON point, 2dsphere index)	Spherical	Provides the same functionality as $nearoperation that  uses GeoJSON point and a2dsphere index. For spherical queries, it may be preferable to use$nearSphere which explicitly specifies the spherical queries in the name rather than $near operator.
$nearSphere (legacy coordinates, 2d index)	Spherical	Use GeoJSON points instead.
$geoWithin : { $geometry: … }	Spherical
$geoWithin : { $box: … }	Flat
$geoWithin : { $polygon: … }	Flat
$geoWithin : { $center: … }	Flat
$geoWithin : { $centerSphere: … }	Spherical
$geoIntersects	Spherical
geoNear (2dsphere index)	Spherical
geoNear (2d index)	Flat
$geoNear (2dsphere index)	Spherical
$geoNear (2d index)	Flat

 

 

Example

Create a collection places with the following documents:

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db.places.insert( {

    name: "Central Park",

   location: { type: "Point", coordinates: [ -73.97, 40.77 ] },

   category: "Parks"

} );

db.places.insert( {

   name: "Sara D. Roosevelt Park",

   location: { type: "Point", coordinates: [ -73.9928, 40.7193 ] },

   category: "Parks"

} );

db.places.insert( {

   name: "Polo Grounds",

   location: { type: "Point", coordinates: [ -73.9375, 40.8303 ] },

   category: "Stadiums"

} );

The following operation creates a 2dsphere index on the location field:

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db.places.createIndex( { location: "2dsphere" } )

The following query uses the $near operator to return documents that are at least 1000 meters from and at most 5000 meters from the specified GeoJSON point, sorted in order from nearest to farthest:

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db.places.find(

   {

     location:

       { $near:

          {

            $geometry: { type: "Point",  coordinates: [ -73.9667, 40.78 ] },

            $minDistance: 1000,

            $maxDistance: 5000

          }

       }

   }

)

The following operation uses the geoNear command to return documents that match the query filter {category: "Parks" }, sorted in order of nearest to farthest to the specified GeoJSON point:

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db.runCommand(

   {

     geoNear: "places",

     near: { type: "Point", coordinates: [ -73.9667, 40.78 ] },

     spherical: true,

     query: { category: "Parks" }

   }

)

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