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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If you have postgis already sitting around then it’s
pretty quick just to try it and see. I’m assuming you’re
talking 20sec for everything, all 170K features? A spatial index doesn’t
buy you anything in the ‘all’ case. That is a lot of features to
display at once and I wonder if one can even make sense of that much detail. A
common technique would be display reduced or somehow generalized versions of
the data at that level and then hit the detailed data as a user zooms in.
Without knowing the data how you’d do that would vary. For example, you
could actually rasterize the data and display the pre-rendered raster version small
scales. Or you might be able to thin the data a bit. Lots of options.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Steve<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
mapserver-users-bounces@lists.osgeo.org
[mailto:mapserver-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>Chris
Jackson<br>
<b>Sent:</b> Thursday, September 02, 2010 3:29 PM<br>
<b>To:</b> P Kishor<br>
<b>Cc:</b> mapserver-users@lists.osgeo.org<br>
<b>Subject:</b> Re: [mapserver-users] Display performance<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Hi<br>
<br>
20 secs is from turning the layer on in the interface. The data is a
model grid as polygons, the file size is about 40mb. I agree 20secs is
too long - I am a web developer in general and know users are fickle! The
other layers load v.quickly so happy in general with performance of smaller
model grids.<br>
<br>
The same layer in an old arcgis server app loads a few secs quicker (from SDE
rather than file) and we just accepted it was just 'one of those things' and
deadlines got in the way - mmm... <br>
<br>
The app is living on a reasonable specced server living in a data centre and
the old web app has been serving the offshore renewables industry fine for a
couple of years or so, just have a need to move to an open source
solution. I was trying to get a feel whether moving to PostGIS rather
than local file will speed things up - I get the feeling it is marginal.<br>
<br>
Maybe I am missing another processing trick (admittedly I have done minimal
work bar a spatial index).<br>
<br>
Thanks for the swift response.<br>
Chris <o:p></o:p></p>
<div>
<p class=MsoNormal>On 2 September 2010 21:07, P Kishor <<a
href="mailto:punk.kish@gmail.com">punk.kish@gmail.com</a>> wrote:<o:p></o:p></p>
<div>
<p class=MsoNormal style='margin-bottom:12.0pt'>On Thu, Sep 2, 2010 at 3:03 PM,
Chris Jackson <<a href="mailto:webturtles@gmail.com">webturtles@gmail.com</a>>
wrote:<br>
> Steve<br>
><br>
> That saves some work, but how long would you expect one that size to load?<br>
> I have just realised (admittedly not looked at the data for a couple of<br>
> years) that it is actually 170,000 records - takes about 20 secs to load -<br>
> sound reasonable?<br>
<br>
<o:p></o:p></p>
</div>
<p class=MsoNormal>What does "to load" mean? Is 20 seconds the time
elapsed from when the<br>
user clicks on the browser to when the user sees the resulting image?<br>
<br>
You are ripping through 170K features and creating an image. 20<br>
seconds seems like a lot. How big and complicated are those features?<br>
How big is the shapefile, in physical size (MB, KB).<br>
<br>
What kind of computer are you using?<br>
<br>
What other processes are running?<br>
<br>
So many variables...<br>
<br>
in any case, if you have a web app, and you want your users to remain<br>
interested in it, you probably will want to bring down the time "to<br>
load" to sub-second, or, at the most a few seconds. You will also want<br>
to consider multiple users -- acceptable performance with one user<br>
might translate into horrendous performance with several concurrent<br>
users.<o:p></o:p></p>
<div>
<p class=MsoNormal><br>
<br>
<br>
<br>
><br>
> Chris<br>
><br>
> On 2 September 2010 20:50, Lime, Steve D (DNR) <<a
href="mailto:Steve.Lime@state.mn.us">Steve.Lime@state.mn.us</a>><br>
> wrote:<br>
>><br>
>> That’s not that big a dataset. Probably faster from a local shapefile.<br>
>><br>
>><br>
>><br>
>> Steve<br>
>><br>
>><br>
>><br>
>> From: <a href="mailto:mapserver-users-bounces@lists.osgeo.org">mapserver-users-bounces@lists.osgeo.org</a><br>
>> [mailto:<a href="mailto:mapserver-users-bounces@lists.osgeo.org">mapserver-users-bounces@lists.osgeo.org</a>]
On Behalf Of Chris Jackson<br>
>> Sent: Thursday, September 02, 2010 2:29 PM<br>
>> To: <a href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><br>
>> Subject: [mapserver-users] Display performance<br>
>><br>
>><br>
>><br>
>> Hi<br>
>><br>
>> I wondered if anyone knew if displaying a 50,000 polygon dataset would
be<br>
>> significantly faster if called from a database rather than a spatially<br>
>> indexed shapefile, or is it a similar overhead for both.<br>
>> Thanks<br>
>> Chris<br>
><o:p></o:p></p>
</div>
<p class=MsoNormal>> _______________________________________________<br>
> mapserver-users mailing list<o:p></o:p></p>
<div>
<p class=MsoNormal>> <a href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><o:p></o:p></p>
</div>
<p class=MsoNormal>> <a
href="http://lists.osgeo.org/mailman/listinfo/mapserver-users" target="_blank">http://lists.osgeo.org/mailman/listinfo/mapserver-users</a><br>
><br>
><br>
<br>
<br>
<br>
--<br>
Puneet Kishor <a href="http://www.punkish.org" target="_blank">http://www.punkish.org</a><br>
Carbon Model <a href="http://carbonmodel.org" target="_blank">http://carbonmodel.org</a><br>
Charter Member, Open Source Geospatial Foundation <a href="http://www.osgeo.org"
target="_blank">http://www.osgeo.org</a><br>
Science Commons Fellow, <a
href="http://sciencecommons.org/about/whoweare/kishor" target="_blank">http://sciencecommons.org/about/whoweare/kishor</a><br>
Nelson Institute, UW-Madison <a href="http://www.nelson.wisc.edu"
target="_blank">http://www.nelson.wisc.edu</a><br>
-----------------------------------------------------------------------<br>
Assertions are politics; backing up assertions with evidence is science<br>
=======================================================================<o:p></o:p></p>
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