Geospatial Indexes and Queries¶
MongoDB offers a number of indexes and query mechanisms to handle geospatial information. This section introduces MongoDB’s geospatial features. For complete examples of geospatial queries in MongoDB, see Geospatial Index Tutorials.
Before storing your location data and writing queries, you must decide the type of surface to use to perform calculations. The type you choose affects how you store data, what type of index to build, and the syntax of your queries.
MongoDB offers two surface types:
To calculate geometry over an Earth-like sphere, store your location data on a spherical surface and use 2dsphere index.
Store your location data as GeoJSON objects with this coordinate-axis order: longitude, latitude. The coordinate reference system for GeoJSON uses the WGS84 datum.
If you choose spherical surface calculations, you store location data as either:
New in version 2.4: Support for GeoJSON storage and queries is new in version 2.4. Prior to version 2.4, all geospatial data used coordinate pairs.
MongoDB supports the following GeoJSON objects:
MongoDB’s geospatial query operators let you query for:
MongoDB can query for locations contained entirely within a specified polygon. Inclusion queries use the $geoWithin operator.
Both 2d and 2dsphere indexes can support inclusion queries. MongoDB does not require an index for inclusion queries after 2.2.3; however, these indexes will improve query performance.
MongoDB can query for locations that intersect with a specified geometry. These queries apply only to data on a spherical surface. These queries use the $geoIntersects operator.
Only 2dsphere indexes support intersection.
MongoDB provides the following geospatial index types to support the geospatial queries.
2dsphere indexes support:
- Calculations on a sphere
- GeoJSON objects and include backwards compatibility for legacy coordinate pairs.
- A compound index with scalar index fields (i.e. ascending or descending) as a prefix or suffix of the 2dsphere index field
New in version 2.4: 2dsphere indexes are not available before version 2.4.
Geospatial Indexes and Sharding¶
You cannot use a geospatial index as the shard key index.
You can create and maintain a geospatial index on a sharded collection if using fields other than shard key.
The following pages provide complete documentation for geospatial indexes and queries:
- 2dsphere Indexes
- A 2dsphere index supports queries that calculate geometries on an earth-like sphere. The index supports data stored as both GeoJSON objects and as legacy coordinate pairs.
- 2d Indexes
- The 2d index supports data stored as legacy coordinate pairs and is intended for use in MongoDB 2.2 and earlier.
- Haystack Indexes
- A haystack index is a special index optimized to return results over small areas. For queries that use spherical geometry, a 2dsphere index is a better option than a haystack index.
- 2d Index Internals
- Provides a more in-depth explanation of the internals of geospatial indexes. This material is not necessary for normal operations but may be useful for troubleshooting and for further understanding.