ST_IsValid

Description

Test if an ST_Geometry value is well-formed in 2D according to the OGC rules. For geometries that are invalid, the PostgreSQL NOTICE will provide details of why it is not valid. For geometries with 3 and 4 dimensions, the validity still only tested in 2 dimensions.

For the version with flags, supported flags are documented in ST_IsValidDetail This version does not print a NOTICE explaining invalidity.

For more information on the definition of geometry validity, refer to "Ensuring OpenGIS compliancy of geometries"

	SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

Performed by the GEOS module.

The version accepting flags is available starting with 2.0.0.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.9

	Neither OGC-SFS nor SQL-MM specifications include a flag argument for ST_IsValid. The flag is a PostGIS extension.

Examples

SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line,
	ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly
--results
NOTICE:  Self-intersection at or near point 0 0
 good_line | bad_poly
-----------+----------
 t         | f

See Also

ST_IsSimple , ST_IsValidReason , ST_IsValidDetail , ST_Summary