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<P><FONT SIZE=2>Thanks for your answer. I have tried this before.</FONT>
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<P><FONT SIZE=2>SELECT COUNT(a.id) FROM tbl1 a, tbl1 b WHERE a.geom && b.geom and a.id <> b.id</FONT>
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<P><FONT SIZE=2>But the result differs from my other query. Regarding to the PostGIS doc at <A HREF="http://postgis.refractions.net/docs/ch06.html" TARGET="_blank">http://postgis.refractions.net/docs/ch06.html</A> the && operator does not check the spatial overlap of two geometries, it checks if the bounding boxes of thw geometries overlap. But in my case I need to check if two geometries spatially overlap. Perhaps there is a possibility to make this faster in some way.</FONT></P>
<P><FONT SIZE=2>Regards, Thorsten</FONT>
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<P><FONT SIZE=2>-----Ursprüngliche Nachricht-----</FONT>
<BR><FONT SIZE=2>Von: postgis-users-bounces@postgis.refractions.net</FONT>
<BR><FONT SIZE=2>[<A HREF="mailto:postgis-users-bounces@postgis.refractions.net">mailto:postgis-users-bounces@postgis.refractions.net</A>]</FONT>
<BR><FONT SIZE=2>Gesendet: Freitag, 25. Mai 2007 09:55</FONT>
<BR><FONT SIZE=2>An: PostGIS Users Discussion</FONT>
<BR><FONT SIZE=2>Betreff: Re: [postgis-users] Overlaps query</FONT>
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<P><FONT SIZE=2>postgis-users-bounces@postgis.refractions.net wrote on 25/05/2007 09.41.05:</FONT>
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<P><FONT SIZE=2>> Hi,</FONT>
<BR><FONT SIZE=2>> I want to query a geometry column using the PostGIS function</FONT>
<BR><FONT SIZE=2>> 'overlaps'. The query shoult return the number of overlapping</FONT>
<BR><FONT SIZE=2>> geometries in a table.</FONT>
<BR><FONT SIZE=2>> Here is the query I tried:</FONT>
<BR><FONT SIZE=2>> SELECT COUNT(a.id) FROM tbl1 a, tbl1 b WHERE OVERLAPS(a.geom, b.</FONT>
<BR><FONT SIZE=2>> geom) AND a.id <> b.id</FONT>
<BR><FONT SIZE=2>> When I run the query, it takes a long time (96528ms) until PostGIS</FONT>
<BR><FONT SIZE=2>> returns the result although my table only contains 10 rows. Is there</FONT>
<BR><FONT SIZE=2>> a possibility to increase the performance of this query?</FONT>
<BR><FONT SIZE=2>> Regards,</FONT>
<BR><FONT SIZE=2>> Thorsten</FONT>
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<P><FONT SIZE=2>Hi! I think you should use the && operator (a.the_geom && b.the_geom)</FONT>
<BR><FONT SIZE=2>instead of the overlaps function (it doesn't use the GIST index, don't know</FONT>
<BR><FONT SIZE=2>why) . I had the same problem, and the query went faster!</FONT>
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<P><FONT SIZE=2>Bye,</FONT>
<BR><FONT SIZE=2>Flavio</FONT>
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