[postgis-devel] [PostGIS] #926: ST_GeometryN, ST_PointN (input of array) return set

PostGIS trac at osgeo.org
Fri Apr 29 05:22:32 PDT 2011

#926: ST_GeometryN, ST_PointN (input of array) return set
 Reporter:  robe         |       Owner:  pramsey      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.0.0
Component:  postgis      |     Version:  trunk        
 Keywords:               |  

Comment(by bitner):

 I am not sure that I would have a preference between returning an array
 and using unnest and just returning a SET. I think the reason that both of
 us are interested in having this is to be able to rely on implementing
 things quickly in SQL/PLPGSQL (not to mention this would make things also
 more easy to parse into arrays of coordinates that could be passed into

 One thing that might be a convenience option would to be able to specify
 an index range in addition to using an array (ie pointn(geom,5,10) as
 equivalent to pointn(geom,{5,6,7,8,9,10}). One nice trick that could be
 done using your generate_series approach could be thinning a line by using
 st_pointn(geom,generate_series(1,st_numpoints(geom),3)) to just get every
 third point.

Ticket URL: <http://trac.osgeo.org/postgis/ticket/926#comment:3>
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