PostGIS

PostGIS
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8.10.2. Distance Operators

Name

PostGIS — Returns the n-D distance between A and B bounding boxes.

Synopsis

double precision +`*`PostGIS`*`(` geometry `+A , geometry B );

Description

The <<#>> operator returns distance between two floating point bounding boxes, possibly reading them from a spatial index (PostgreSQL 9.1+ required). Useful for doing nearest neighbor approximate distance ordering.

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText('POINT(1 2)') PostGIS geom) instead of g1.geom PostGIS.

Availability: 2.2.0 — KNN only available for PostgreSQL 9.1+

PostGIS

Name

Synopsis

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See Also