[postgis-tickets] [PostGIS] #4736: ST_NumGeometries is zero for GeometryCollection with empty parts

[PostGIS]

#4736: ST_NumGeometries is zero for GeometryCollection with empty parts
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  Reporter:  Mike Taves  |      Owner:  strk
      Type:  defect      |     Status:  assigned
  Priority:  medium      |  Milestone:  PostGIS 3.0.4
 Component:  postgis     |    Version:  2.4.x
Resolution:              |   Keywords:
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Comment (by pramsey):

 The overloading of ST_NumGeometries to return non-null on simple geometry
 means that we end up with an odd situation where behaviours are slightly
 different with respect to element counts on empty things. I feel like the
 below is the least disruptive thing that involves the least change.
 {{{
 ST_NumGeometries('POINT EMPTY') => 1
 ST_NumGeometries('GEOMETRYCOLLECTION EMPTY') => 0
 ST_NumGeometries('GEOMETRYCOLLECTION(POINT EMPTY)') => 1
 ST_GeometryN('POINT EMPTY', 1) => POINT EMPTY
 ST_GeometryN('GEOMETRYCOLLECTION EMPTY', 1) => NULL
 ST_GeometryN('GEOMETRYCOLLECTION(POINT EMPTY)', 1) => POINT EMPTY
 }}
 So just adjusting the return of ST_NumGeometries to be non-zero for
 collections of empty sub-elements.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4736#comment:8>
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