[mapserver-users] MapServer Oracle performance

[Frank Warmerdam]

Ivan wrote:
> Debugging those two process I noticed some important difference. shp2img 
> calls GDALDatasetRasterIO and will ultimately calls the driver IRasterIO 
> but without calling GetOverview first, so when it goes to the driver 
> IReadBlock the level is 0. gdal_translate calls GetOverview and get the 
> appropriated level but it does not touch the driver IRasterIO, it goes 
> directly to the IReadBlock with the correct level. It Seams like QGIS 
> does the same.

Ivan,

Yikes!  On review I have reason to believe the GDALDataset::RasterIO()
method is not using overviews!  I will investigate on this side as well.

I only very recently reworked the MapServer IO code to use
GDALDataset::RasterIO() instead of calls to GDALRasterBand::RasterIO()
so this isn't a problem that would have showed up in MapServer in the past.

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