[Qgis-developer] slow raster loading

Giovanni Manghi giovanni.manghi at gmail.com
Tue Aug 9 16:10:02 EDT 2011


Hi Paolo, Tim

unfortunately in the last months I had a very little time to follow the
developments, so maybe I will say obvious things.

I just compiled QGIS master under Ubuntu against GDAL 1.8 and when
loading a raster I see the same message

Warning: Object::connect: No such signal
QgsGdalProvider::statusChanged( QString )
in /home/gio/qgis-Quantum-GIS-6a1073f/src/core/raster/qgsrasterlayer.cpp:2446

the practical difference I see is that, as Tim describes, that rasters
are slower to open the first time, but then are faster as before, if not
more. This seems to me not a big deal when opening quite small images,
but it can be when opening multiple images at one time or when adding
very big rasters.

For instance I have 3GB landsat images with overviews that before these
changes opened in a nick of time, now -the first time- they take a few
seconds (10/15).

The same images without overviews before the changes took 10/15 seconds
to open, now -the first time- it takes much more.

Another issue I guess can be if the rasters are stored in a place where
the aux.xml cannot be written.

I guess that the right behaviour is the new one, but maybe it is worth
add an option to avoid collecting stats on raster load?

cheers

-- Giovanni --



On Tue, 2011-08-09 at 15:49 +0200, Paolo Cavallini wrote:
> Hi all.
> With current master, I get bad performances in loading rasters (a <12Mb takes >5
> sec); when double-clicking it from the QGIS browser, it is far slower (>20 sec). From
> the console:
> Warning: Object::connect: No such signal QgsGdalProvider::statusChanged( QString ) in
> /storage/build/Quantum-GIS/src/core/raster/qgsrasterlayer.cpp:2446
> Any hint?
> All the bes



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