ST_IsRing — Tests if a LineString is closed and simple.
boolean ST_IsRing(
geometry g)
;
Returns TRUE
if this
LINESTRING
is both ST_IsClosed
(ST_StartPoint(g) ~= ST_Endpoint(g)
) and ST_IsSimple (does not self intersect).
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 defines the result of
|
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)