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Yes, I have tried doing the selection with a triangle, and it also
works, but there is another bug in GEOS, that makes it EXTREMELY slow
for any geometries with +2000 points.<br>
<br>
I have posted some info on trac about it:<br>
<a class="moz-txt-link-freetext" href="http://trac.osgeo.org/mapguide/ticket/172">http://trac.osgeo.org/mapguide/ticket/172</a><br>
<br>
So, the original problem is "fixed", but it opens another problem,
which may have more to do with GEOS than with the provider.<br>
I think the related speed problem makes the provider more useless with
the fix than without.<br>
<br>
I can build a new provider, but I don't have the setup for Oracle and
PostGIS.<br>
<br>
<pre class="moz-signature" cols="72">Regards, Kenneth, GEOGRAF A/S
</pre>
<br>
<br>
Traian Stanev skrev:
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<title>[mapguide-users] OGR / GEOS selection problem</title>
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<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Hi.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">I
checked in a temporary fix to this problem. I simply warped one
of the coordinates of the input polygon by 10^-10. This is sufficient
to make
OGR call GEOS to compute the exact intersection. Selection should work
correctly
now in the AJAX viewer.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">I
have not posted a compiled DLL yet, so Kenneth feel free to do
so, (-:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Traian<o:p></o:p></span></p>
<p class="MsoNormal"><span
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<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">
<a class="moz-txt-link-abbreviated" href="mailto:mapguide-users-bounces@lists.osgeo.org">mapguide-users-bounces@lists.osgeo.org</a>
[<a class="moz-txt-link-freetext" href="mailto:mapguide-users-bounces@lists.osgeo.org">mailto:mapguide-users-bounces@lists.osgeo.org</a>] <b>On Behalf Of </b>Traian
Stanev<br>
<b>Sent:</b> Thursday, June 07, 2007 3:46 PM<br>
<b>To:</b> MapGuide Users Mail List; MapGuide Users Mail List<br>
<b>Subject:</b> RE: [mapguide-users] OGR / GEOS selection problem<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi Kenneth,<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Thanks for tracking this down. I would try to
fix this by
bypassing Geos. FDO has utility code that can check for an
intersection. We
could take the BBOX result and pass that through a real intersection
check on
the provider side. This way the intersection check would be performed
only on
geometries that are close enough to the query polygon so the overhead
should
not be too bad.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Traian<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom: 12pt;"><span
style="font-size: 10pt;">-----Original
Message----- <br>
<b>From:</b> <a class="moz-txt-link-abbreviated" href="mailto:mapguide-users-bounces@lists.osgeo.org">mapguide-users-bounces@lists.osgeo.org</a> on behalf
of Kenneth, GEOGRAF A/S <br>
<b>Sent:</b> Thu 6/7/2007 2:54 AM <br>
<b>To:</b> MapGuide Users Mail List <br>
<b>Cc:</b> <br>
<b>Subject:</b> [mapguide-users] OGR / GEOS selection problem</span><o:p></o:p></p>
</div>
<p><span style="font-size: 10pt;">Maciej previously reported
problems with the
OGR provider using PostGIS.<br>
<br>
The problem is with the OGR provider.<br>
Se the Trac ticket for details:<br>
<a moz-do-not-send="true"
href="http://trac.osgeo.org/mapguide/ticket/172">http://trac.osgeo.org/mapguide/ticket/172</a><br>
<br>
I have posted some follow up on the issue, but in hope someone knows a<br>
lot about GEOS, I'm also posting it here:<br>
<br>
<br>
I have been examining the problem, using a custom build of the OGR<br>
provider. It is true that without GEOS support in OGR, the Intersect<br>
only does a BBOX check.<br>
<br>
However, merely enabling GEOS will not work, as the viewer sends a<br>
square that is orthogonal to the axes (like a BBOX). The GEOS library<br>
will interpret this as another BBOX, and only perform the BBOX check<br>
anyway.<br>
<br>
When I change the polgyon sent from the viewer to a triangle, it takes<br>
22 seconds to calculate the Intersects result with a polygon with 8000<br>
linesegments. I have a 2+ GHz machine.<br>
<br>
It seems that GEOS always builds a full intersection matrix, before<br>
returning the result. This is obviously not optimal for a simple hit<br>
test. Even with this knowledge, I still don't see how it can take 22<br>
seconds to calculate 8000 * 3 intersections.<br>
<br>
Can someone explain this, or how to fix it?<br>
<br>
<br>
<br>
--<br>
Regards, Kenneth, GEOGRAF A/S<br>
<br>
<br>
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