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- 2dsphere Indexes
2dsphere Indexes¶
New in version 2.4.
Overview¶
A 2dsphere index supports queries that calculate geometries on an earth-like sphere. 2dsphere index supports all MongoDB geospatial queries: queries for inclusion, intersection and proximity. See the Geospatial Query Operators for the query operators that support geospatial queries.
The 2dsphere index supports data stored as GeoJSON objects and as legacy coordinate pairs (See also 2dsphere Indexed Field Restrictions). For legacy coordinate pairs, the index converts the data to GeoJSON Point. For details on the supported GeoJSON objects, see GeoJSON Objects.
The default datum for an earth-like sphere is WGS84. Coordinate-axis order is longitude, latitude.
2dsphere (Version 2)¶
Changed in version 2.6.
MongoDB 2.6 introduces a version 2 of 2dsphere indexes. Version 2 is the default version of 2dsphere indexes created in MongoDB 2.6 and later series. To override the default version 2 and create a version 1 index, include the option { "2dsphereIndexVersion": 1 } when creating the index.
sparse Property¶
Changed in version 2.6.
2dsphere (Version 2) indexes are sparse by default and ignores the sparse: true option. If a document lacks a 2dsphere index field (or the field is null or an empty array), MongoDB does not add an entry for the document to the index. For inserts, MongoDB inserts the document but does not add to the 2dsphere index.
For a compound index that includes a 2dsphere index key along with keys of other types, only the 2dsphere index field determines whether the index references a document.
Earlier versions of MongoDB only support 2dsphere (Version 1) indexes. 2dsphere (Version 1) indexes are not sparse by default and will reject documents with null location fields.
Additional GeoJSON Objects¶
2dsphere (Version 2) includes support for additional GeoJSON object: MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection. For details on all supported GeoJSON objects, see GeoJSON Objects.
Considerations¶
geoNear and $geoNear Restrictions¶
The geoNear command and the $geoNear pipeline stage require that a collection have at most only one 2dsphere index and/or only one 2d index whereas geospatial query operators (e.g. $near and $geoWithin) permit collections to have multiple geospatial indexes.
The geospatial index restriction for the geoNear command and the $geoNear pipeline stage exists because neither the geoNear command nor the $geoNear pipeline stage syntax includes the location field. As such, index selection among multiple 2d indexes or 2dsphere indexes is ambiguous.
No such restriction applies for geospatial query operators since these operators take a location field, eliminating the ambiguity.
Shard Key Restrictions¶
You cannot use a 2dsphere index as a shard key when sharding a collection. However, you can create and maintain a geospatial index on a sharded collection by using a different field as the shard key.
2dsphere Indexed Field Restrictions¶
Fields with 2dsphere indexes must hold geometry data in the form of coordinate pairs or GeoJSON data. If you attempt to insert a document with non-geometry data in a 2dsphere indexed field, or build a 2dsphere index on a collection where the indexed field has non-geometry data, the operation will fail.
Create a 2dsphere Index¶
To create a 2dsphere index, use the db.collection.createIndex() method, specifying the location field as the key and the string literal "2dsphere" as the index type:
db.collection.createIndex( { <location field> : "2dsphere" } )
Unlike a compound 2d index which can reference one location field and one other field, a compound 2dsphere index can reference multiple location and non-location fields.
For the following examples, consider a collection places with documents that store location data as GeoJSON Point in a field named loc:
db.places.insert(
{
loc : { type: "Point", coordinates: [ -73.97, 40.77 ] },
name: "Central Park",
category : "Parks"
}
)
db.places.insert(
{
loc : { type: "Point", coordinates: [ -73.88, 40.78 ] },
name: "La Guardia Airport",
category : "Airport"
}
)
Create a 2dsphere Index¶
The following operation creates a 2dsphere index on the location field loc:
db.places.createIndex( { loc : "2dsphere" } )
Create a Compound Index with 2dsphere Index Key¶
A compound index can include a 2dsphere index key in combination with non-geospatial index keys. For example, the following operation creates a compound index where the first key loc is a 2dsphere index key, and the remaining keys category and names are non-geospatial index keys, specifically descending (-1) and ascending (1) keys respectively.
db.places.createIndex( { loc : "2dsphere" , category : -1, name: 1 } )
Unlike the 2d index, a compound 2dsphere index does not require the location field to be the first field indexed. For example:
db.places.createIndex( { category : 1 , loc : "2dsphere" } )