[PostGIS] #5828: Performace issue in ST_DFullyWithin

[PostGIS]

#5828: Performace issue in ST_DFullyWithin
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  Reporter:  nbvfgh   |      Owner:  pramsey
      Type:  defect   |     Status:  new
  Priority:  blocker  |  Milestone:  PostGIS 3.6.0
 Component:  postgis  |    Version:  3.5.x
Resolution:           |   Keywords:
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Comment (by nbvfgh):

 It may not be necessary to actually calculate the buffer for extending the
 distance of geometry A to determine whether geometry B is fully included
 in the buffer for extending the distance of geometry A. Because in
 reality, the point on geometry A that is closest to geometry B is the one
 that determines whether geometry B is fully included in the buffer zone of
 the extended distance of geometry A. We refer to this point as **P1**.

 So, we can simplify this problem as "**Is geometry B completely contained
 within the buffer zone of the extended distance from point P1?**" And the
 buffer zone of a point is a circle, and we only need to consider its
 radius. Under what circumstances does a circle contain a geometry? We call
 the point on geometry B that is farthest from point P1 as **P2**, and
 finally simplify the problem as "**Is the distance between P1 and P2 less
 than the distance?**".

 Finally, we can obtain the following equivalent formula:
 {{{ST_DFullyWithin(A, B, R) <=> ST_Contains(ST_Buffer(A, R), B) <=>
 ST_MaxDistance(ST_ClosestPoint(A, B), B) ≤ R}}}

 Sorry for the lengthy explanation, and thank you for your patience.
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5828#comment:1>
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