[postgis-tickets] [PostGIS] #5563: Potential bug in the ST_Equals function.

[PostGIS]

#5563: Potential bug in the ST_Equals function.
---------------------+---------------------------
 Reporter:  Wenjing  |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 3.4.1
Component:  postgis  |    Version:  3.4.x
 Keywords:           |
---------------------+---------------------------
 Consider the following test case:

 {{{
 SELECT ST_Equals(Foo.a, Foo.b), ST_Distance(Foo.a, Foo.c)
     FROM (SELECT ST_GeomFromText('LINESTRING(2 0, 0 1)') As a,
     ST_GeomFromText('LINESTRING(2 0, 0.2 0.9, 0 1)') As b,
     ST_GeomFromText('POINT( 0.2 0.9)') As c) As Foo; -- expected: {t},
 actual: {f}
 }}}

 The distance from point c ('POINT( 0.2 0.9)') to line a ('LINESTRING(2 0,
 0 1)') is 0. Line b ('LINESTRING(2 0, 0.2 0.9, 0 1)') is plus.

 Line a should equal line b because they have the same points set. { (x,y)
 | 2*x + y = 0 }

 **Actual behavior**: PostGIS doesn’t consider LINE a to be equal to LINE
 b. The result of st_equals is false which means Postgis doesn’t consider
 they are the same line, although the distance between them calculated is
 0.

 The issue cannot be reproduced with integers only, indicating a potential
 floating-point issue. After all coordinate points are magnified ten times,
 the results are in line with expectations.

 Additional Information[https://tarry-goal-613.notion.site/Potential-bug-
 in-the-ST_Equals-function-398b8876ee9842219cb872e7eb7bb546?pvs=4]
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5563>
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