[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 3.4.2
Component:  postgis                 |    Version:  3.4.x
 Keywords:  mvt, self-intersection  |
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 I'm trying to generate a vector tile layer of a linestring consisting of
 four points (you could use more than four points but this is just a
 simplified example). Here is the linestring in geojson
 (https://gist.github.com/mhkeller/9a65553c28d5063b45817b7d996b59c3)

 The second and the fourth points are the same, so the line doubles back on
 itself. When I use this query
 (https://gist.github.com/mhkeller/05d7eafc43966a2b3b5b2d41784b300b) in a
 tile server, the third point in the line string is missing.

 I've made a full but simple reproduction with photos here:
 https://github.com/mhkeller/postgis-line-repro

 I also tried using the dirt-simple-postgis-http-api
 (https://github.com/tobinbradley/dirt-simple-postgis-http-api) instead of
 the one I wrote and I get the same result.

 However, if I generate the tiles using geojson2mvt
 (https://github.com/NYCPlanning/labs-geojson2mvt), the line renders
 correctly. A stack exchange user reported that generating the tiles with
 MapTiler also renders the line correctly
 (https://gis.stackexchange.com/questions/471851/missing-line-segment-when-
 serving-a-vector-tile-from-postgis#comment772175_471851).
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5654>
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