ST_CollectionHomogenize function to homogenize a GeometryCollection - ApsaraDB RDS

ST_CollectionHomogenize returns the simplest representation of the content of a GeometryCollection.

Syntax

geometry ST_CollectionHomogenize(geometry collection);

Parameter	Description
`collection`	The geometry object that you want to specify.

The function processes input geometry as follows:

Singleton collection: A collection containing a single atomic element is returned as that atomic element.
Homogeneous collection: A collection of the same geometry type is returned as the corresponding MULTI type (for example, MULTILINESTRING).

Homogeneous collection converted to a MULTI geometry

A collection of two LINESTRINGs is returned as a MULTILINESTRING.

SELECT ST_AsText(
  ST_CollectionHomogenize(
    ST_GeomFromText('GEOMETRYCOLLECTION(LINESTRING(1 1,2 1),LINESTRING(2 1,2 2))')
  )
);

              st_astext
--------------------------------------
 MULTILINESTRING((1 1,2 1),(2 1,2 2))
(1 row)