AW: Re: [Qgis-user] QGIS mapserver performance

[Nicklas Avén]

I don't think it sounds that strange. Rendering directly from a binary
stream straight from PostGIS should be much faster than going through a
webserver, creating an image and sending that image to QGIS.


What to check is if the spatial index is properly used by QGIS
Mapserver. Maybe it is using the whole layer for even smaller parts of
the map.

Another thing that often makes a big differnce in performance for wms is
what image format you are requesting. It can vary a little what is
fastest depending on how much colors is involved and how homogeneous the
image is.

But going through a wms-service can never be as fast as rendering the
binary stream dierctly.

Regards
Nicklas


On Mon, 2011-03-21 at 08:46 +0100, Andreas Neumann wrote:
> hm - strange.
> 
>  If it works fast in QGIS, it should work equally fast in QGIS server. 
>  There shouldn't be any difference.
> 
>  Something to investigate - maybe with Marco.
> 
>  Are there any messages in the Apache log files (access log or error 
>  log?)
> 
>  Andreas
> 
>  On Mon, 21 Mar 2011 08:38:49 +0100, Ziegler Stefan wrote:
> > Scalix message content
> > Hi Andi
> >
> >> What exactly do you mean by "rendering straight from postgis"? What
> >> software is rendering straight from Postgis? UMN Mapserver, or what
> >> other renderer? Or your own renderer?
> > No, "straight from postgis" means adding the layer in QGIS from
> > postgis. I save this qgis project and make it available as WMS. Since
> > there is only QGIS (as renderer) involved I thought there would not 
> > be
> > a big performance difference. Ok, there is apache who is handling the
> > cgi request but that won't take 4 seconds.
> >
> >> There are some performance bottlenecks regarding clipping of
> >> larger/more
> >> complex polygons. Marco can tell you more.
> > I don't think it's a clipping issue since it's fast when adding the
> > same layer 'straight from postgis' :) So there must be some 
> > additional
> > work when making a detour.
> >
> > regards
> > Stefan
> >
> >>
> >> Andreas
> >>
> >> On 3/20/11 2:44 PM, Ziegler Stefan wrote:
> >> > Hi
> >> >
> >> > I have some questions concerning the performance of qgis
> >> mapserver: Using layers with a small amount of polygons I do
> >> not see a big difference between rendering the same layer
> >> straight from postgis and from local qgis mapserver
> >> installation. For a layer with some 400'000 polygons it takes
> >> approx. 4 seconds from qgis mapserver (even for large scales
> >> with only some polygons to render). But it only takes some
> >> fractions of a second when the layer is rendered straight
> >> from postgis (and growing with smaller scales -> more polyons).
> >> >
> >> > Everything is running on a dual core laptop. So there
> >> should be no big download bottleneck. No special styles are
> >> applied to the layers (just a simple fill and an outline).
> >> Are there some requests in addition to "GetMap"? Or what's
> >> responsible for this big difference?
> >> >
> >> > regards
> >> > Stefan
> >> >
> >> > Mit freundlichem Gruss
> >> > Stefan Ziegler
> >> > Leiter amtliche Vermessung
> >> >
> >> > Amt für Geoinformation
> >> > Rötistrasse 4
> >> > 4501 Solothurn
> >> > 032 627 75 96
> >> > _______________________________________________
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> >> > Qgis-user at lists.osgeo.org
> >> > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >>
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