[PostGIS] #5654: Missing line segment with self-intersection and MVT

[PostGIS]

#5654: Missing line segment with self-intersection and MVT
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  Reporter:  mhkeller  |      Owner:  pramsey
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS 3.4.3
 Component:  postgis   |    Version:  3.4.x
Resolution:            |   Keywords:  mvt, self-intersection
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Comment (by tjcaverly):

 `SELECT postgis_full_version()`

 `POSTGIS="3.3.2 4975da8" [EXTENSION] PGSQL="140" GEOS="3.9.0-CAPI-1.16.2"
 PROJ="7.2.1" LIBXML="2.9.10" LIBJSON="0.15" LIBPROTOBUF="1.3.3"
 WAGYU="0.5.0 (Internal)"`

 I get the same result as you,

 {{{
 select st_astext(
     st_simplify(
     'LINESTRING (2 2,3 2,4 1,3 2, 4 4)'
     ,0)
     );

 "LINESTRING(2 2,3 2,4 4)"
 }}}

 This incorrectly removes the 3rd point, erasing a large portion of the
 geometry. It then removes the 4th point since it's the same as the 2nd,
 which doesn't affect anything. Correct behavior would be returning
 `LINESTRING (2 2,3 2,4 1,3 2, 4 4)`.

 The example on stackexchange is different but shows the same bug.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5654#comment:6>
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