Geospatial queries

Query based on geographic data

Redis Stack's geospatial feature allows you to query for data associated with geographic locations. You can either query for locations within a specific radius or based on geometric shapes, such as polygons. A polygon shape could, for instance, represent a lake or the layout of a building.

The examples in this article use the following schema:

Radius

You can construct a radius query by passing the center coordinates (longitude, latitude), the radius, and the distance unit to the FT.SEARCH command.

FT.SEARCH index "@geo_field:[lon lat radius unit]"

Allowed units are m, km, mi, and ft.

The following query finds all bicycle stores within a radius of 20 miles around London:

FT.SEARCH idx:bicycle "@store_location:[-0.1778 51.5524 20 mi]"

Shape

The only supported shapes are points and polygons. You can query for polygons or points that either contain or are within a given geometric shape.

FT.SEARCH index "@geo_shape_field:[{WITHIN|CONTAINS} $shape] PARAMS 2 shape "shape_as_wkt" DIALECT 3

Here is a more detailed explanation of this query:

1. Field name: you need to replace geo_shape_field with the GEOSHAPE field's name on which you want to query.
2. Spatial operator: spatial operators define the relationship between the shapes in the database and the shape you are searching for. You can either use WITHIN or CONTAINS. WITHIN finds any shape in the database that is inside the given shape. CONTAINS queries for any shape that surrounds the given shape.
3. Parameter: the query refers to a parameter named shape. You can use any parameter name here. You need to use the PARAMS clause to set the parameter value. The value follows the well-known text representation of a geometry. Supported types are POINT(x y) and POLYGON((x1 y1, x2 y2, ...)).
4. Dialect: Shape-based queries have been available since version three of the query dialect.

The following example query verifies if a bicycle is within a pickup zone:

FT.SEARCH idx:bicycle "@pickup_zone:[CONTAINS $bike]" PARAMS 2 bike "POINT(-0.1278 51.5074)" DIALECT 3

If you want to find all pickup zones that are approximately within Europe, then you can use the following query:

FT.SEARCH idx:bicycle "@pickup_zone:[WITHIN $europe]" PARAMS 2 europe "POLYGON((-25 35, 40 35, 40 70, -25 70, -25 35))" DIALECT 3