[postgis-tickets] [PostGIS] #3030: ST_Boundary does not reduce dimensionality for empty geometries

[PostGIS]

#3030: ST_Boundary does not reduce dimensionality for empty geometries
----------------------------+-----------------------------------------------
 Reporter:  bladeoflight16  |       Owner:  pramsey
     Type:  defect          |      Status:  new    
 Priority:  medium          |   Milestone:         
Component:  postgis         |     Version:  2.1.x  
 Keywords:                  |  
----------------------------+-----------------------------------------------
 This query:

 {{{
 SELECT ST_AsText(ST_Boundary(geom))
 FROM (VALUES ('POLYGON EMPTY'::GEOMETRY),
              ('MULTIPOLYGON EMPTY'::GEOMETRY),
              ('LINESTRING EMPTY'::GEOMETRY),
              ('MULTILINESTRING EMPTY'::GEOMETRY)
      ) g (geom);
 }}}

 gives these results:

 {{{
 'POLYGON EMPTY'
 'MULTIPOLYGON EMPTY'
 'LINESTRING EMPTY'
 'MULTILINESTRING EMPTY'
 }}}

 I generally expect ST_Boundary to return a geometry of one less dimension
 even if the geometry is an empty one. (I.e., I expect an empty linestring
 from a polygon input and an empty point for a linestring input.)

 (Posting this after being instructed to on the mailing list.)

 Confirmed using the following versions:
 POSTGIS="2.1.5 r13152" GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.7.1, 23
 September 2009" GDAL="GDAL 1.9.0, released 2011/12/29" LIBXML="2.8.0"
 LIBJSON="UNKNOWN" RASTER

 and

 "POSTGIS="2.1.4 r12966" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6
 March 2012" GDAL="GDAL 1.9.2, released 2012/10/08" LIBXML="2.7.6"
 LIBJSON="UNKNOWN" RASTER"

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/3030>
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.