ST_Polygonize

Introduction: Generates a GeometryCollection composed of polygons that are formed from the linework of an input GeometryCollection. When the input does not contain any linework that forms a polygon, the function will return an empty GeometryCollection.

Note

ST_Polygonize function assumes that the input geometries form a valid and simple closed linestring that can be turned into a polygon. If the input geometries are not noded or do not form such linestrings, the resulting GeometryCollection may be empty or may not contain the expected polygons.

Format: ST_Polygonize(geom: Geometry)

Example:

SELECT ST_AsText(ST_Polygonize(ST_GeomFromEWKT('GEOMETRYCOLLECTION (LINESTRING (2 0, 2 1, 2 2), LINESTRING (2 2, 2 3, 2 4), LINESTRING (0 2, 1 2, 2 2), LINESTRING (2 2, 3 2, 4 2), LINESTRING (0 2, 1 3, 2 4), LINESTRING (2 4, 3 3, 4 2))')));

Output:

GEOMETRYCOLLECTION (POLYGON ((0 2, 1 3, 2 4, 2 3, 2 2, 1 2, 0 2)), POLYGON ((2 2, 2 3, 2 4, 3 3, 4 2, 3 2, 2 2)))