[PostGIS] #6089: wrong node used when adding a new long line

[PostGIS]

#6089: wrong node used when adding a new long line
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  Reporter:  Lars Aksel Opsahl  |      Owner:  strk
      Type:  defect             |     Status:  new
  Priority:  medium             |  Milestone:
 Component:  topology           |    Version:  master
Resolution:                     |   Keywords:  snap
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Comment (by strk):

 Replying to [comment:8 Lars Aksel Opsahl]:
 > What happens is that lower node is used i my testcase.

 When I test this _BOTH_ nodes are used, not ONLY the lower one. And that's
 because _BOTH_ nodes are within the given tolerance.

 > I also assume in this case the result should be equal when I run
 tolerance -1 or 1e-07 , related what nodes that are selected in this case.
 Running with -1 it snaps to upper node and not the lower node as when
 using 1e-07.

 Passing -1 asks PostGIS to compute the "minimum distance that can be
 represented with a 64bit floating point number between the further-from-0
 vertex outward". I guess such distance (which I didn't check what it is)
 must be bigger than the distance between the incoming line and the upper
 node (which is computed by PostGIS as 0).

 > The problem is not invalid topology, but that result i sliver topology
 that I have to remove later again.

 At least you can spot and remove that sliver !

 What I'm saying is that this is all expected behavior, not a bug, not
 "wrong".
 If you want to turn this ticket to a feature request we can keep it open,
 but maybe it would be cleaner to file a new ticket when there's a clear
 plan.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/6089#comment:9>
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