[PostGIS] #6120: XX000: SQL/MM Spatial exception - curve not simple

[PostGIS]

#6120: XX000: SQL/MM Spatial exception - curve not simple
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  Reporter:  Lars Aksel Opsahl  |      Owner:  strk
      Type:  defect             |     Status:  new
  Priority:  medium             |  Milestone:  PostGIS 3.6.5
 Component:  topology           |    Version:  3.6.x
Resolution:                     |   Keywords:
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Comment (by strk):

 Another interesting workaround: pass 0 as the tolerance to
 `TopoGeo_addLinestring` when adding the final offending line (it also
 works with the originally attached testcase by swapping -1 with 0 in the
 last argument of the last line).

 Passing -1 as we are doing in the testcase doesn't mean "use 0 tolerance"
 but "use automatically computed tolerance" which in our case is much
 larger than the distance between the existing line and the incoming line:
 `2.49528570556641e-13`.
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/6120#comment:7>
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