[postgis-tickets] [PostGIS] #2242: ST_Union in aggregate form treats NULL as EMPTY

[PostGIS]

#2242: ST_Union in aggregate form treats NULL as EMPTY
---------------------------+------------------------------------------------
 Reporter:  gabrimonfa     |       Owner:  robe         
     Type:  defect         |      Status:  new          
 Priority:  medium         |   Milestone:  PostGIS 2.0.4
Component:  documentation  |     Version:  2.0.x        
 Keywords:                 |  
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Changes (by robe):

  * owner:  pramsey => robe
  * component:  postgis => documentation
  * milestone:  => PostGIS 2.0.4


Comment:

 The general rule is that NULLs are simply ignored in aggregates (so its
 not  empty), its as if the record is just not there.  So PostGIS works as
 expected.

 ST_Union(geom1,geom2) IS NOT an aggregate and as such it doesn't throw
 away anything. In fact it doesn't even go into the function because its
 marked as a STRICT (meaning any NULL inputs result in NULL out).

 I'll just flag this as a documentation issue to be clarified, but IT IS by
 design.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2242#comment:2>
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