[PostGIS] #5722: Spatial exception - geometry boundary touches interior of edge 4 (XX000)

[PostGIS]

#5722: Spatial exception - geometry boundary touches interior of edge 4 (XX000)
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  Reporter:  strk      |      Owner:  strk
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS 3.5.0
 Component:  topology  |    Version:  master
Resolution:            |   Keywords:
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Comment (by strk):

 [[Image(screen01.png)]]

 New analisys: upon adding the vertical line GEOS correctly computes nodes
 but PostGIS is unable to tell that the node falls on the edge. Logs:

 {{{
 [topo/lwgeom_topo.c:_lwt_AddPoint:6536] Adding point:
 POINT(-0.350498072243138 0.326335974301659)
 [topo/lwgeom_topo.c:_lwt_AddPoint:6612] New point is within
 1.26179306007529e-15 units of 0 edges
 [topo/lwgeom_topo.c:lwt_GetFaceContainingPoint:7479] Closest segment on
 edge 2 is 1 (dist 8.28391e-18)
 DEBUG:  [topo/lwgeom_topo.c:lwt_GetFaceContainingPoint:7482] Closest
 segment on edge 2 is LINESTRING(8.13909 0.334123, -11.9641 0.315684)
 }}}

 What the logs say is a contradiction:

  1. The point is NOT within 1.24e-15 units from the edge
  2. The point is at 8.28e-18 distance from the edge

 Either 1 or 2 is true, cannot both be true.

  - _lwt_AddPoint (1) uses ST_DWithin to find edges within distance, which
 gives the wrong answer, in this case.
  - lwt_GetFaceContainingPoint (2) uses the <-> operator to find the
 closest edge and ptarray_closest_segment_2d to compute the distance.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5722#comment:6>
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