[postgis-tickets] [PostGIS] #4252: Revise gidx_merge behavior with unknown

[PostGIS]

#4252: Revise gidx_merge behavior with unknown
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  Reporter:  komzpa       |      Owner:  Komzpa
      Type:  enhancement  |     Status:  assigned
  Priority:  medium       |  Milestone:  PostGIS 3.0.0
 Component:  postgis      |    Version:  trunk
Resolution:               |   Keywords:
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Comment (by komzpa):

 I think for WKB we already do POINT EMPTY as POINT (NaN, NaN). If we apply
 same thinking here, GIDX(NaN NaN, NaN NaN) will be a box for such a thing,
 and it will give the relation we want with all the functions:

  * gidx_merge(GIDX(NaN NaN, NaN NaN), GIDX(1 2, 3 4)) -> GIDX(1 2, 3 4)
  * overlaps(GIDX(NaN NaN, NaN NaN), GIDX(1 2, 3 4)) -> False
  * overlaps(GIDX(NaN NaN, NaN NaN), GIDX(NaN NaN, NaN NaN)) -> False
  * intersects(GIDX(NaN NaN, NaN NaN), GIDX(1 2, 3 4)) -> False
  * intersects((GIDX(NaN NaN, NaN NaN), GIDX(NaN NaN, NaN NaN))) -> False

 And there will be no need to special case the undefined/empty across all
 functions. Any invariant that breaks this way?

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4252#comment:2>
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