PostGIS
Description
Given a geometry collection, returns the "simplest" representation of the contents.
-
Homogeneous (uniform) collections are returned as the appropriate multi-geometry.
-
Heterogeneous (mixed) collections are flattened into a single GeometryCollection.
-
Collections containing a single atomic element are returned as that element.
-
Atomic geometries are returned unchanged. If required, these can be converted to a multi-geometry using ST_Multi.
|
Availability: 2.0.0
Examples
Single-element collection converted to an atomic geometry
SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0))'));
st_astext
------------
POINT(0 0)Nested single-element collection converted to an atomic geometry:
SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(MULTIPOINT((0 0)))'));
st_astext
------------
POINT(0 0)Collection converted to a multi-geometry:
SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))'));
st_astext
---------------------
MULTIPOINT((0 0),(1 1))Nested heterogeneous collection flattened to a GeometryCollection:
SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0), GEOMETRYCOLLECTION( LINESTRING(1 1, 2 2)))'));
st_astext
---------------------
GEOMETRYCOLLECTION(POINT(0 0),LINESTRING(1 1,2 2))Collection of Polygons converted to an (invalid) MultiPolygon:
SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION (POLYGON ((10 50, 50 50, 50 10, 10 10, 10 50)), POLYGON ((90 50, 90 10, 50 10, 50 50, 90 50)))'));
st_astext
---------------------
MULTIPOLYGON(((10 50,50 50,50 10,10 10,10 50)),((90 50,90 10,50 10,50 50,90 50)))