[mapserver-users] MapServer Oracle performance

[Frank Warmerdam]

Ivan wrote:
> I setup an very simple MAP file with a GDAL/GeoRaster as the DATA 
> parameter of a layer like that:
> 
>   LAYER
>     DATA "geor:scott/tiger at orcl,CITIES,SCENE,ID=120"
> 
> This raster is 14336x14336x3 big (600Mb) and has 7 level of pyramids on 
> it. The question is that, because of the pyramids (= GDAL overviews) 
> this image loads, pan and zoom pretty fast on QuantumGIS with the Oracle 
> Raster plugin but that doesn't help at all in MapServer.
> 
> I might not be that familiar with MapServer architecture either, but it 
> looks to me that it doesn't take advantage of Pyramids at all. Not even 
> if the raster is stored in MrSID. The only way to go is to build tile 
> cache. Right?

Ivan,

MapServer certainly should be taking advantage of overviews if they are
available.  MapServer just calls RasterIO and lets it do the downsampling
so if GDAL's RasterIO is downsampling with overviews it should be good.

If this is not working, we should likely be investigating how the overviews
are presented by the driver.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent