[PostGIS] #5868: Add Function to Detect Valid Polygons with Point Touching Rings

[PostGIS]

#5868: Add Function to Detect Valid Polygons with Point Touching Rings
---------------------------+---------------------------
  Reporter:  gravitystorm  |      Owner:  pramsey
      Type:  defect        |     Status:  new
  Priority:  medium        |  Milestone:  PostGIS 3.5.3
 Component:  postgis       |    Version:  3.4.x
Resolution:                |   Keywords:
---------------------------+---------------------------
Comment (by pramsey):

 {{{

 CREATE OR REPLACE FUNCTION internal_rings_do_not_touch_exterior(polygon
 geometry)
 RETURNS boolean AS
 $$
 DECLARE
     ring_record record;
     exterior geometry;
     interior geometry;
 BEGIN
     -- Ensure input is a polygon
     IF GeometryType(polygon) NOT IN ('POLYGON', 'MULTIPOLYGON') THEN
         RAISE EXCEPTION 'Input must be a POLYGON or MULTIPOLYGON';
     END IF;

     -- Dump rings into a loop
     FOR ring_record IN SELECT * FROM ST_DumpRings(polygon)
     LOOP
         IF ring_record.path[1] = 0 THEN
             -- First ring is the exterior
             exterior := ST_ExteriorRing(ring_record.geom);
         ELSE
             -- Check if this internal ring touches the exterior
             interior := ST_ExteriorRing(ring_record.geom);
             IF ST_Intersects(interior, exterior) THEN
                 RETURN FALSE;  -- Found a touching internal ring
             END IF;
         END IF;
     END LOOP;

     -- No touching rings found
     RETURN TRUE;
 END;
 $$ LANGUAGE plpgsql IMMUTABLE;
 }}}
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5868#comment:7>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.