ST_IsValid — Returns true if the ST_Geometry is well formed.


boolean ST_IsValid(geometry g);


Test if an ST_Geometry value is well formed. For geometries that are invalid, the PostgreSQL NOTICE will provide details of why it is not valid. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"


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

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


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
NOTICE:  Self-intersection at or near point 0 0
 good_line | bad_poly
 t         | f

See Also

ST_IsSimple, ST_IsValidReason, ST_Summary