[postgis-tickets] [PostGIS] #2474: [raster]: ST_Union that takes 2 rasters

[PostGIS]

#2474: [raster]: ST_Union that takes 2 rasters
-------------------------+--------------------------------------------------
 Reporter:  robe         |       Owner:  dustymugs    
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.2.0
Component:  raster       |     Version:  trunk        
 Keywords:               |  
-------------------------+--------------------------------------------------
 I'm finding myself constantly needing to do a union of just two rasters.
 So I often end up doing ugly things like


 {{{
 SELECT ST_Union(f.rast)
 FROM (SELECT rast
 FROM table1 INNER JOIN table2 ON ST_Intersects(table1.rast,1,table2.geom)
 WHERE table2.gid =1
 UNION ALL
 SELECT ST_AsRaster(somegeom, rast,100)
 FROM ST_Intersects(table1.rast,1,table2.geom)
 WHERE table2.gid = 1) As f
 }}}

 When all I want to do is this

 {{{
 SELECT ST_Union(rast, ST_AsRaster(somegeom,rast) )
 FROM table1 INNER JOIN table2
  ON ST_Intersects(rast,1, table2.geom)
 WHERE table2.gid = 1
 }}}



 In theory I could use MapAlgebra but MapAlgebra blows my mind with all the
 permutations of it.

 Note geometry has an ST_Union(geom1,geom2) so it would be in line with
 what we do with geometry already except we'd have an optional
 expression type

 So I'm think the proto would look like


 {{{

 ST_Union(rast1,rast2, expressiontype = 'LAST')
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2474>
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