geometry-expression.ST_IsValid()

By default, the server does not validate spatial data as it is created or imported from other formats. The ST_IsValid method can be used to verify that the imported data represents a geometry that is valid. Operations on invalid geometries return undefined results.

• ST_IsSimple method for type ST_Geometry

The following returns the result 0 because the polygon contains a bow tie (the ring has a self-intersection).

SELECT ST_Geometry::ST_GeomFromText( 'Polygon(( 0 0, 4 0, 4 5, 0 -1, 0 0 ))' )
	.ST_IsValid()

The following returns the result 0 because the polygons within the geometry self-intersect at a surface. Self-intersections of a geometry collection at finite number of points is considered valid.

SELECT ST_Geometry::ST_GeomFromText( 
            'MultiPolygon((( 0 0, 2 0, 1 2, 0 0 )),((0 2, 1 0, 2 2, 0 2)))' )
	            .ST_IsValid()