[PostGIS] #5811: Failed Z-axis tolerance in ST_RemoveRepeatedPoints

[PostGIS]

#5811: Failed Z-axis tolerance in ST_RemoveRepeatedPoints
---------------------+---------------------------
 Reporter:  nbvfgh   |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  high     |  Milestone:  PostGIS 3.5.1
Component:  postgis  |    Version:  3.5.x
 Keywords:           |
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 I have been using a fuzzer to test PostGIS recently.


 I used a function called ST_RemoveRepeatedPoint, which takes two
 parameters, a geometry and a floating-point tolerance. When I tried to use
 this function to delete two points that are equal on x and y but not equal
 on the z-axis, a possible logical error occurred:


 ST_RemoveRepeatedPoint(geometry geom, float8 tolerance): Returns a version
 of the given geometry with duplicate consecutive points removed. The
 function processes only (Multi)LineStrings, (Multi)Polygons and
 MultiPoints but it can be called with any kind of geometry.If the
 tolerance parameter is provided, vertices within the tolerance distance of
 one another are considered to be duplicates.


 Query statement:



 {{{
 SELECT ST_AsText(ST_RemoveRepeatedPoints('**MULTIPOINT(10 10 10, 10 10
 13)**', 2));
 }}}



 The result is:
 {{{
 MULTIPOINT Z ((10 10 13))
 }}}



 It is obvious that the difference between the two points in MULTIPOINT (10
 10 10, 10 10 13) on the z-axis is 3, and neither point should be deleted.


 And the query statement:



 {{{
 SELECT ST_AsText(ST_RemoveRepeatedPoints('MULTIPOINT(10 10 10, 13 10 10)',
 2));
 }}}


 These two points only differ on the x-axis and are 3，resulting in
 {{{
 MULTIPOINT Z ((13 10 10),(10 10 10))
 }}}

 No point was deleted, this is the correct result.


 In the official documentation of Postgis, ST_RemoveRepeatedPoints is
 stated as a function that supports 3D, but it seems to be invalid for
 tolerance on the z-axis.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5811>
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