Descrição

Retorna VERDADEIRO se essa LINESTRING for ST_IsClosed (ST_StartPoint(g) ~= ST_Endpoint(g)) e ST_IsSimple (não cruzar consigo mesma).

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 o resultado do ST_IsRing(NULO) para ser 0, enquanto o PostGIS retorna NULO.

Exemplos

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)

Veja também

ST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint