[postgis-tickets] [PostGIS] #5258: Linestring empty when intersecting vertical line with a square

[PostGIS]

#5258: Linestring empty when intersecting vertical line with a square
-----------------------------+---------------------------
 Reporter:  cactusbone       |      Owner:  pramsey
     Type:  defect           |     Status:  new
 Priority:  medium           |  Milestone:  PostGIS 3.3.2
Component:  postgis          |    Version:  3.2.x
 Keywords:  ST_Intersection  |
-----------------------------+---------------------------
 Hello, I've stumbled on something weird :

 Using
 {{{
 SELECT ST_Astext(
         ST_Intersection(
                 ST_GeomFromText('LINESTRING(1 1, 1 2)'),
                 ST_GeomFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))')
         )
 )
 }}}

 returns `LINESTRING EMPTY`

 on PostGIS 3.2 (`"POSTGIS=""3.2.3 2f97b6c"" [EXTENSION] PGSQL=""140""
 GEOS=""3.9.0-CAPI-1.16.2"" SFCGAL=""1.3.8"" PROJ=""7.2.1"" GDAL=""GDAL
 3.2.2, released 2021/03/05"" LIBXML=""2.9.10"" LIBJSON=""0.15""
 LIBPROTOBUF=""1.3.3"" WAGYU=""0.5.0 (Internal)"" RASTER"` or
 `"POSTGIS=""3.2.1 5fae8e5"" [EXTENSION] PGSQL=""140""
 GEOS=""3.9.0-CAPI-1.16.2"" SFCGAL=""1.3.8"" PROJ=""7.2.1"" GDAL=""GDAL
 3.2.2, released 2021/03/05"" LIBXML=""2.9.10"" LIBJSON=""0.15""
 LIBPROTOBUF=""1.3.3"" WAGYU=""0.5.0 (Internal)"" TOPOLOGY RASTER"`)

 It works on PostGIS 2.5 (`"POSTGIS=""2.5.1 r17027"" [EXTENSION]
 PGSQL=""110"" GEOS=""3.7.1-CAPI-1.11.1 27a5e771"" SFCGAL=""1.3.6""
 PROJ=""Rel. 5.2.0, September 15th, 2018"" GDAL=""GDAL 2.4.0, released
 2018/12/14"" LIBXML=""2.9.4"" LIBJSON=""0.12.1"" LIBPROTOBUF=""1.2.1""
 TOPOLOGY RASTER"`)

 It's the same with horizontal lines
 {{{
 SELECT ST_Astext(
         ST_Intersection(
                 ST_GeomFromText('LINESTRING(1 1, 2 1)'),
                 ST_GeomFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))')
         )
 )
 }}}

 However it works when the line is neither horizontal nor vertical or when
 it touches the intersection

 Queries that work:
 {{{
 SELECT ST_Astext(ST_Intersection(
         ST_GeomFromText('LINESTRING(1 1, 2 2)'),
         ST_GeomFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))')
 ))
 }}}
 {{{
 SELECT ST_Astext(ST_Intersection(
         ST_GeomFromText('LINESTRING(1 1, 2 1.000000000001)'),
         ST_GeomFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))')
 ))
 }}}
 {{{
 SELECT ST_Astext(
         ST_Intersection(
                 ST_GeomFromText('LINESTRING(0 0, 0 1)'),
                 ST_GeomFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))')
         )
 )
 }}}
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5258>
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