ST_IsRing

Introduction: RETURN true if LINESTRING is ST_IsClosed and ST_IsSimple.

Format: ST_IsRing(geom: geometry)

Return type: Boolean

SQL example:

SELECT ST_IsRing(ST_GeomFromText('LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'))

Output: true