Oracle的ST_Boundary

Question

是否有可能使用Oracle来执行相当于ST_Boundary的操作？从多边形得到一个LINESTRING/MULTILINESTRING，还是从LINESTRING获得一个多点？

我知道其他供应商支持它：

Boundary.html

https://learn.microsoft.com/en-us/sql/t-sql/spatial-geometry/stboundary-geometry-data-type?view=sql-server-ver16

Answer 1

要获得边界，请参见UTIL.POLYGONTOLINE

在fn中没有内置的linestring到multipoint。但是这里有一个简单的fn来完成它(假设为2D)：

CREATE OR REPLACE FUNCTION multipoint_from_line (line_geom SDO_GEOMETRY)
   RETURN SDO_GEOMETRY DETERMINISTIC PARALLEL_ENABLE IS

   multipoint SDO_GEOMETRY := NULL;
BEGIN
   IF line_geom IS NOT NULL
   THEN
     multipoint := line_geom;

     IF multipoint.sdo_ordinates.count = 0
     THEN
       multipoint := NULL;
     ELSE
       multipoint.sdo_gtype := 2005;
       multipoint.sdo_elem_info := 
sdo_elem_info_array(1,1,multipoint.sdo_ordinates.count/2);
     END IF;
   END IF;

   return multipoint;
END;
/

-- Calling from SQL
SELECT multipoint_from_line 
(sdo_geometry(2002,4326,null,sdo_elem_info_array(1,2,1),sdo_ordinate_array(0,0,1,1,3,3)))
FROM dual;

-- Calling from PL/SQL
DECLARE
   multipoint SDO_GEOMETRY;
BEGIN
   multipoint := multipoint_from_line 
(sdo_geometry(2002,4326,null,sdo_elem_info_array(1,2,1),sdo_ordinate_array(0,0,1,1,3,3)));
END;
/