Descripción

Devuelve TRUE si esta LINESTRING es ST_IsClosed (ST_StartPoint(g) ~= ST_Endpoint(g)) y ST_IsSimple (no se intersecta con ella misma).

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

2.1.5.1

This method implements the SQL/MM specification.

SQL-MM 3: 7.1.6

	SQL-MM define que el resultado de ST_IsRing(NULL) debe ser 0, mientras que PostGIS devuelve NULL.

Ejemplos

SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 t         | t           | t
(1 row)

SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 f         | t           | f
(1 row)

Ver también

ST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint