[postgis-tickets] [PostGIS] #4127: ST_Dimension returns 0 for empty GeometryCollection

[PostGIS]

#4127: ST_Dimension returns 0 for empty GeometryCollection
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  Reporter:  esparano  |      Owner:  pramsey
      Type:  defect    |     Status:  closed
  Priority:  medium    |  Milestone:  PostGIS 2.4.5
 Component:  postgis   |    Version:  2.4.x
Resolution:  fixed     |   Keywords:
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Changes (by robe):

 * status:  reopened => closed
 * resolution:   => fixed


Comment:

 Here is the way I see it

 ST_Dimension is a concept of a geometry's geometric type and is defined to
 be the maximum dimension of any geometry in the set.

 So that said

 POINT EMPTY -> 0
 LINESTRING EMPTY -> 1
 MULTIPOLYGON EMPTY -> 2
 SELECT ST_Dimension(ST_Collect('POLYGON EMPTY'::geometry, 'LINESTRING
 EMPTY'::geometry)) -> 2

 So the only question left is what to do about GEOMETRYCOLLECTION EMPTY.
 Does an empty geometrycollection imply we should consider it being the
 highest dimension of emptiness or the lowest dimension of emptiness?


 I frankly don't care - doesn't seem to be worth changing the code to
 address a questionably ambiguous thing
 and making it return -1 is liable to break someone's code somewhere, so
 would have to wait til PostGIS 3.0 since it is a policy change.

 That said, I'm reclosing this bug.  If you want to discuss further, about
 why this is all wrong,
 use our dev mailing list for that:

 https://lists.osgeo.org/mailman/listinfo/postgis-devel

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4127#comment:6>
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