ST_Polygonize-ApsaraDB RDS(RDS)-阿里云帮助中心

An aggregate function that builds possible polygons from a set of linework geometries and returns them as a GeometryCollection.

Syntax

geometry ST_Polygonize(geometry set geomField);
geometry ST_Polygonize(geometry[] geomArray);

Parameters

Parameter	Description
`geomField`	The geometry column in the input dataset. Used when calling the function as an aggregate over a result set.
`geomArray`	An array of geometry objects from which polygons are formed.

Usage notes

The constituent lines of each input geometry must be correctly noded before calling this function. Unnoded input produces incomplete or incorrect polygon output.
Most third-party tools do not support GeometryCollection results. Use ST_Dump to expand the collection into individual polygon rows.

Examples

The following example passes four LINESTRING geometries that form a closed square. ST_Polygonize assembles them into a single polygon and returns it inside a GeometryCollection.

SELECT ST_AsText(
    ST_Polygonize(
        ARRAY[
            'LINESTRING(0 0,0 1)'::geometry,
            'LINESTRING(0 1,1 1)'::geometry,
            'LINESTRING(1 1,1 0)'::geometry,
            'LINESTRING(0 0,1 0)'::geometry
        ]
    )
);

Result:

              st_astext
----------------------------------------------------
 GEOMETRYCOLLECTION(POLYGON((0 0,0 1,1 1,1 0,0 0)))
(1 row)