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<TITLE>RE: [postgis-users] touches function problem</TITLE>
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<P><FONT SIZE=2>Make sure you have indexes created on the geometry, and have run ANALYZE ... if that;s done and doesn't show any difference, perhaps using a "distance(x,y) = 0" construct might be faster. In some cases it is faster and in some not.<BR>
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You might also post the table definitions (including indexes), table sizes (# of rows) and the results of your query when run under "EXPLAIN ANALYZE <...>;" ... the explain analyze tells a lot about the strategy that PostgreSQL is using. It is possible that the slow part is not the spatial query.<BR>
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HTH,<BR>
<BR>
Greg Williamson<BR>
Senior DBA<BR>
GlobeXplorer LLC, a DigitalGlobe company<BR>
<BR>
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-----Original Message-----<BR>
From: postgis-users-bounces@postgis.refractions.net on behalf of caij@lreis.ac.cn<BR>
Sent: Tue 11/13/2007 4:42 AM<BR>
To: postgis-users@postgis.refractions.net<BR>
Subject: [postgis-users] touches function problem<BR>
<BR>
Hi all,<BR>
I have a table which has 279,370 records.And the geometry type is polygon and multipolygon.When I used the touches function to get the neighbor polygons of one polygon,it takes me 7-10 seconds to process it.And to my program,it is unbearable. (the processing sentence is below!) Who can tell me how to improve the speed?<BR>
Wait for ur answers!<BR>
Good Luck!<BR>
<BR>
select astext(wkb_geometry),ogc_fid,ischanged,prechanged,nrings(wkb_geometry) as nrings,numgeometries(wkb_geometry) as numgeometries from (select ogc_fid,wkb_geometry,ischanged,prechanged from quanbj1_10000_6_9_fullscreen where wkb_geometry && (select wkb_geometry from quanbj1_10000_6_9_fullscreen where ogc_fid=149648 ) and (level=1) or (level>1 and isleaf=1) or (level>1 and child_level<1 )) as temprec where touches(wkb_geometry,(select wkb_geometry from quanbj1_10000_6_9_fullscreen where ogc_fid=149648))<BR>
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