[Qgis-developer] slow raster loading

[Peter Borissow]

Hi Tim-
    I understand that the stats are only gathered when needed. Still, I think users should have the option to compute stats and possibly other support files on load. This could be accomplished via a preference/setting or a pop-up dialog. In theory, you could have a thread pool to generate the support files in the background. The size of the thread pool could be determined by a user preference/setting.


Just a thought.

Take Care,

Peter



________________________________
From: Tim Sutton <lists at linfiniti.com>
To: Peter Borissow <peter.borissow at yahoo.com>
Cc: Frank Warmerdam <warmerdam at pobox.com>; qgis-developer <qgis-developer at lists.osgeo.org>
Sent: Wednesday, August 10, 2011 5:46 AM
Subject: Re: [Qgis-developer] slow raster loading

Hi

On Wed, Aug 10, 2011 at 12:20 AM, Peter Borissow
<peter.borissow at yahoo.com> wrote:
> Also, might be a good idea to spawn a separate thread to generate the aux
> file in the background...
>

It could be a possibility but the way things are set up now, stats are
only gathered when really needed, and if you need then for the
activity you are doing you would have to wait for them anyway. The
only merrit of using a separate thread would be if we decided to start
gathering complete stats on first load of a raster in the background
always so that they are preemptively there when the user does
something that needs stats. However I don't know if that is a good
idea - if you have many rasters in a project that need stats it will
spawn many threads and the IO / CPU overhead may be unpleasant.

Regards

Tim

>
> ________________________________
> From: Frank Warmerdam <warmerdam at pobox.com>
> To: Tim Sutton <lists at linfiniti.com>
> Cc: qgis-developer <qgis-developer at lists.osgeo.org>
> Sent: Tuesday, August 9, 2011 5:51 PM
> Subject: Re: [Qgis-developer] slow raster loading
>
> On Tue, Aug 9, 2011 at 2:37 PM, Tim Sutton <lists at linfiniti.com> wrote:
>>
>> 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.
>
> Tim, and others,
>
> By the way, there is a mechanism in GDAL to support storing .aux.xml
> information in an alternative directory when the file cannot be
> created on the target directory due to permissions, read-only media, etc.
>
> This is enabled by setting the GDAL_PAM_PROXY_DIR option to
> point to a directory where files can be written.  If there is a place
> known to QGIS that would be good for this, it might make sense
> to take advantage of this.
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Software Developer
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>
>



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