[postgis-tickets] [PostGIS] #5117: aggregate st_union ignores linestring of zero length

[PostGIS]

#5117: aggregate st_union ignores linestring of zero length
----------------------+---------------------------
  Reporter:  anneb    |      Owner:  pramsey
      Type:  defect   |     Status:  closed
  Priority:  medium   |  Milestone:  PostGIS 3.3.0
 Component:  postgis  |    Version:  3.2.x
Resolution:  invalid  |   Keywords:
----------------------+---------------------------
Changes (by komzpa):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 Zero-length lines are not a valid geometry per OGC spec, the end points of
 line are its boundary and boundary isn't inside the geometry. Some
 interpretations of it will mean "there are no points in line". Any is
 correct as the geometry is not valid.

 {{{
 07:01:59 [kom] > select ST_IsValid(st_geomfromewkt('srid=3857;LINESTRING(5
 5,5 5)'));
 NOTICE:  00000: Too few points in geometry component at or near point 5 5
 LOCATION:  pg_notice, lwgeom_pg.c:364
 ┌────────────┐
 │ st_isvalid │
 ├────────────┤
 │ f          │
 └────────────┘
 (1 row)
 }}}

 You can get result you expect if you make sure your geom is valid.

 {{{

 07:03:22 [kom] > with lines as (
   select ST_MakeValid(st_geomfromewkt('srid=3857;LINESTRING(5 5,5 5)')) as
 geom
   union all
   select ST_MakeValid(st_geomfromewkt('srid=3857;LINESTRING(1 1, 2 2)'))
 as geom
   )
 select ST_AsText(st_union(geom)) from lines;
 ┌────────────────────────────────────────────────────┐
 │                     st_astext                      │
 ├────────────────────────────────────────────────────┤
 │ GEOMETRYCOLLECTION(POINT(5 5),LINESTRING(1 1,2 2)) │
 └────────────────────────────────────────────────────┘
 (1 row)

 Time: 2,638 ms
 }}}

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5117#comment:1>
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