[Qgis-developer] QgisLogger can be a serious bottleneck

[G. Allegri]

Hi Andrea, as I said above I'm not considering it an error.
The topic of this post is QGIS message logging.
The processing completes as expected, with the same results as Spatialite
and PostGIS. These simply do it silently :)

giovanni



2014-07-05 15:59 GMT+02:00 Andrea Peri <aperi2007 at gmail.com>:

> Hi GioHappy,
>
> the empty-collection is absolutelly not necessarylly a bug.
> It is the obviously result of an operation on a machine (like the
> computer) with a binary finite arithmetic.
>
> Usually the empty is due to a too low value to be describe with a
> finite binary arithmetic.
>
> If the dataset is small or it is topologically correct (this not mean
> only to be snapped).
>  the collection results never happened.
> Instead if the dataset is not topologically correct and is big the
> probability to have some collection result grow.
> We tipically have alway an 0.01% of collection on our results.
>
> I suggest you to use directly postgis or spatialite to do this kind of
> operations.
>
> In these products you have the useful tools to resolve the collections
> correctly.
>
> Regard,
>
> Andrea.
>
>
> 2014-07-05 12:40 GMT+02:00 G. Allegri <giohappy at gmail.com>:
> > Hi Jurgen,
> > I wouldn't call them errors. GEOSDIfference returned a lot of empty
> > geomcollections, which the QgsVectorFileWriter couldn't manage.
> Consequently
> > it wrote a log message for each geometry it couldn't write [1].
> >
> > Surely the logging should be improved in this specific case. Anyway, I
> think
> > the option to turn QgsMessageLog off could be useful anyway...
> >
> > giovanni
> >
> > [1]
> >
> https://github.com/qgis/QGIS/blob/master/src/core/qgsvectorfilewriter.cpp#L1718
> >
> >
> > 2014-07-05 12:31 GMT+02:00 Jürgen E. <jef at norbit.de>:
> >
> >> Hi Giovanni,
> >>
> >> On Sat, 05. Jul 2014 at 10:27:24 +0200, G. Allegri wrote:
> >> > As I reported in a previous post, I was unable to conclude a
> difference
> >> > operation on a vector because the tool was running in exponential
> time.
> >>
> >> > Debugging pointed me to the problem: QgsVectoFileWriter was logging
> tons
> >> > of
> >> > empty geometres with an incompatible type which will be discarded.
> >> > After commenting the line of logging the process completed in linear
> >> > time.
> >>
> >> > Shouldn't we offer the opportunity to turn QgsLogger off? This would
> let
> >> > the user/developer to switch it off whenever he already knows what's
> >> > happening.
> >> > Is it already there and I missed it?
> >>
> >> What error message did you get and wouldn't it be better to kill them
> >> where it
> >> origins or to issue a final "%n empty geometries skipped" instead of
> >> logging
> >> individual errors.
> >>
> >> Alternatively we could issue a "last message repeated %n times" in
> message
> >> log
> >> to make it behave better - although that only works the error message
> are
> >> identical.
> >>
> >>
> >> Jürgen
> >>
> >> --
> >> Jürgen E. Fischer           norBIT GmbH             Tel.
> >> +49-4931-918175-31
> >> Dipl.-Inf. (FH)             Rheinstraße 13          Fax.
> >> +49-4931-918175-50
> >> Software Engineer           D-26506 Norden
> >> http://www.norbit.de
> >> QGIS release manager (PSC)  Germany                    IRC: jef on
> >> FreeNode
> >>
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> >
> >
> >
> >
> > --
> > Giovanni Allegri
> > http://about.me/giovanniallegri
> > Twitter: https://twitter.com/_giohappy_
> > blog: http://blog.spaziogis.it
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> >
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>
>
> --
> -----------------
> Andrea Peri
> . . . . . . . . .
> qwerty àèìòù
> -----------------
>



-- 
Giovanni Allegri
http://about.me/giovanniallegri
Twitter: https://twitter.com/_giohappy_
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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