[Qgis-developer] slow raster loading

[Tim Sutton]

Hi

On Tue, Aug 9, 2011 at 10:10 PM, Giovanni Manghi
<giovanni.manghi at gmail.com> wrote:
> 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
>

This may be fixed via a patch given to me by Etienne Sky - please let
me know if it still does it.

> 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.

Yes thats why I was asking if the file permissions exist to write the
aux.xml. If they don't behaviour should be the same as prior to my
native raster stats commits i.e. stats will be recalced each time you
open a project / add a layer and trigger something that needs the
stats.

>
> 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?



Ok I put a fix for this in master- can you tell me if it improves the situation?


Regards

Tim

>
> 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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