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Query a 2d Index

On this page

  • Points within a Shape Defined on a Flat Surface
  • Points within a Circle Defined on a Sphere
  • Proximity to a Point on a Flat Surface
  • Exact Matches on a Flat Surface

The following sections describe queries supported by the 2d index.

To select all legacy coordinate pairs found within a given shape on a flat surface, use the $geoWithin operator along with a shape operator. Use the following syntax:

db.<collection>.find( { <location field> :
{ $geoWithin :
{ $box|$polygon|$center : <coordinates>
} } } )

The following queries for documents within a rectangle defined by [ 0 , 0 ] at the bottom left corner and by [ 100 , 100 ] at the top right corner.

db.places.find( { loc :
{ $geoWithin :
{ $box : [ [ 0 , 0 ] ,
[ 100 , 100 ] ]
} } } )

The following queries for documents that are within the circle centered on [ -74 , 40.74 ] and with a radius of 10:

db.places.find( { loc: { $geoWithin :
{ $center : [ [-74, 40.74 ] , 10 ]
} } } )

For syntax and examples for each shape, see the following:

  • $box

  • $polygon

  • $center (defines a circle)

MongoDB supports rudimentary spherical queries on flat 2d indexes for legacy reasons. In general, spherical calculations should use a 2dsphere index, as described in 2dsphere Indexes.

To query for legacy coordinate pairs in a "spherical cap" on a sphere, use $geoWithin with the $centerSphere operator. Specify an array that contains:

Use the following syntax:

db.<collection>.find( { <location field> :
{ $geoWithin :
{ $centerSphere : [ [ <x>, <y> ] , <radius> ] }
} } )

The following example query returns all documents within a 10-mile radius of longitude 88 W and latitude 30 N. The example converts distance to radians by dividing distance by the approximate equatorial radius of the earth, 3963.2 miles:

db.<collection>.find( { loc : { $geoWithin :
{ $centerSphere :
[ [ 88 , 30 ] , 10 / 3963.2 ]
} } } )

Proximity queries return the legacy coordinate pairs closest to the defined point and sort the results by distance. Use either the $near operator. The operator requires a 2d index.

The $near operator uses the following syntax:

db.<collection>.find( { <location field> :
{ $near : [ <x> , <y> ]
} } )

For examples, see $near.

You cannot use a 2d index to return an exact match for a coordinate pair. Use a scalar, ascending or descending, index on a field that stores coordinates to return exact matches.

In the following example, the find() operation will return an exact match on a location if you have a { 'loc': 1} index:

db.<collection>.find( { loc: [ <x> , <y> ] } )

This query will return any documents with the value of [ <x> , <y> ].

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Create a 2d Index