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

[PostGIS]

#2242: ST_Union in aggregate form treats NULL as EMPTY
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 Reporter:  gabrimonfa  |       Owner:  pramsey
     Type:  defect      |      Status:  new    
 Priority:  medium      |   Milestone:         
Component:  postgis     |     Version:  2.0.x  
 Keywords:              |  
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Comment(by nw):

 Aggregates generally ignore nulls where they wouldn't really
 be meaningful, or keep as a null if that makes sense.
 I would be surprised if ST_Union returned null if one of the
 inputs was null.

 select string_agg(i,', ') from (select generate_series(1,3)::text as i
 union all select null union all  select generate_series(1,3)::text as i)
 as i;
     string_agg
 ------------------
  1, 2, 3, 1, 2, 3
 (1 row)

 I think treating null as empty is the right thing to do here.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2242#comment:1>
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