[postgis-devel] [PostGIS] #1766: ST_RemEdgeModFace: Allows removing shared edges by universal face and a topogeometry

[PostGIS]

#1766: ST_RemEdgeModFace: Allows removing shared edges by universal face and a
topogeometry
----------------------+-----------------------------------------------------
 Reporter:  jomarlla  |       Owner:  strk         
     Type:  defect    |      Status:  new          
 Priority:  medium    |   Milestone:  PostGIS 2.0.1
Component:  topology  |     Version:  trunk        
 Keywords:            |  
----------------------+-----------------------------------------------------
 Layer t3.parcelas with 3 polygons adjacent polygons.


 {{{
 SELECT CreateTopology('t3', 0, 0.1);

 create table t3.parcelas (gid serial primary key, codigo varchar);
 select addtopogeometrycolumn ('t3','t3','parcelas','topogeom','POLYGON');
 INSERT INTO t3.parcelas (codigo, topogeom) VALUES ('A',  totopogeom
 ('MULTIPOLYGON(((0 0, 100 0, 100 100, 0 100, 0 0)))'::geometry, 't3', 1,
 0.1));
 INSERT INTO t3.parcelas (codigo, topogeom) VALUES ('B',  totopogeom
 ('MULTIPOLYGON(((100 0, 200 0, 200 100, 100 100, 100 0)))'::geometry,
 't3', 1, 0.1));
 INSERT INTO t3.parcelas (codigo, topogeom) VALUES ('C',  totopogeom
 ('MULTIPOLYGON(((200 0, 300 0, 300 100, 200 100, 200 0)))'::geometry,
 't3', 1, 0.1));
 }}}

 when I try to remove an edge which is needed by a topogeometry but one of
 the side is the universal polygon (id 0) PostGIS does not throw an error:


 {{{
 select ST_RemEdgeModFace ('t3', 6);
 NOTICE:  Updating next_{right,left}_face of ring edges...
 NOTICE:  Deletion of edge 6 joins faces 2 and 0
  st_remedgemodface
 -------------------
                  0
 }}}

 The topogeometry returns an empty multipolygon:

 select st_astext(topogeom::geometry) from t3.parcelas where gid = 2;
      st_astext
 --------------------
  MULTIPOLYGON EMPTY


 Even though the topogeometry id = 2 exists it does not appear in the
 relation table:


 {{{
 select gid,(topogeom).* from t3.parcelas;
  gid | topology_id | layer_id | id | type
 -----+-------------+----------+----+------
    1 |          30 |        1 |  1 |    3
    2 |          30 |        1 |  2 |    3
    3 |          30 |        1 |  3 |    3

 select * from t3.relation ;

  topogeo_id | layer_id | element_id | element_type
 ------------+----------+------------+--------------
           1 |        1 |          1 |            3
           3 |        1 |          3 |            3

 }}}

 The current behavior (sandro santilli) is:
 "ST_RemEdgeModFace (which you're calling) is required to _modify_
 one face to take up the space previously occupied by the faces this
 edge was separating.

 By convention, when one of the faces is the universal face, the
 _other_ face is kept, while if both faces are not universal, the
 face on the _right_ is kept and the face on the _left_ is remved.

 Now, if you have a TopoGeometry defined by only the face that is
 removed you get an exception, while if you have a TopoGeometry
 defined by the face that is modified, or by both faces, you get
 no exception."

 Probably ST_RemEdgeNewFace is also affected

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1766>
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