[postgis-devel] [PostGIS] #866: [raster] Change the ST_MapAlgebra nodatavalueexpr text parameter for nodatavaluerepl

PostGIS trac at osgeo.org
Tue Oct 18 07:37:42 PDT 2011


#866: [raster] Change the ST_MapAlgebra nodatavalueexpr text parameter for
nodatavaluerepl
----------------------------+-----------------------------------------------
 Reporter:  pracine         |       Owner:  dzwarg       
     Type:  defect          |      Status:  assigned     
 Priority:  blocker         |   Milestone:  PostGIS 2.0.0
Component:  postgis raster  |     Version:  trunk        
 Keywords:                  |  
----------------------------+-----------------------------------------------

Comment(by pracine):

 More explanations:

 -nodatavalueexpr would be an expression possibly containing "rast".

 -nodatavaluerepl is not an expression, it is a constant replacement value
 of type double.

 After analysis (done with David in Mtl) we concluded that it makes no
 sense to pass a nodata value expression (nodatavalueexpr) of "rast" since
 in this case "rast" is always "nodata" and hence a constant. So it is
 better, simpler and makes more sense to just pass a constant "nodata value
 replacement" (nodatavaluerepl).

 Everything would work with nodatavalueexpr. But it makes more sense to
 pass a constant. It is also a bit faster as it does not have to be
 evaluated.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/866#comment:6>
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