[postgis-devel] [PostGIS] #1639: [raster] MapAlgebraExpr can't handle conditions

[PostGIS]

#1639: [raster] MapAlgebraExpr can't handle conditions
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 Reporter:  nicklas  |       Owner:  pracine      
     Type:  defect   |      Status:  new          
 Priority:  high     |   Milestone:  PostGIS 2.0.0
Component:  raster   |     Version:  trunk        
 Keywords:           |  
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Comment(by pracine):

 Replying to [comment:14 nicklas]:
 > If I cast to Integer and put it in '8BSI' like this:
 > Then I would expect the false results to show as 0, right?

 Yes, but still 0 is nodata.

 > But I still get the same result (nodata as I have learned now :-) )

 Seems normal to me.

 > To do this calculation in PostGIS it takes about 45 seconds, but in QGIS
 with the same images as geotiff it takes less than 2 seconds.

 I guess a real comparative test with QGIS would be to open the image and
 make the calculation but yes, we still have a lot of work to do on our map
 algebra to compare with QGIS or Arc.

 > But it can be because PostGIS can't gain fully from the SATA3 ssd on
 this box while maybe the file based  gdal calculation through QGIS can?

 I'm afraid it won't make much difference...

 > Or is it some casts that is giving a false bottleneck?

 We still have to find the bottleneck but I guess it is in the great
 flexibility of our expression parser. With flexibility comes slowiness. We
 will have to think about the avenues we have to make it faster. I think
 there are many.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1639#comment:15>
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