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<p class=MsoNormal><span style='color:#1F497D'>Add a where clause on the
indexed column (presumably f.geometry).<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>WHERE f.geometry&&</span>
geomfromtext('POINT(-9.1533 38.69686)',4326) <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Rob.<o:p></o:p></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='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"'> postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <b>On Behalf Of </b>Pedro
Doria Meunier<br>
<b>Sent:</b> Friday, March 09, 2007 9:04 AM<br>
<b>To:</b> 'PostGIS Users Discussion'<br>
<b>Subject:</b> [postgis-users] optimize query<br>
<b>Importance:</b> High<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi List,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m once again in need of guru advice… <span
style='font-family:Wingdings'>J</span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>This is the query:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>select freguesia, distance(geomfromtext('POINT(-9.1533
38.69686)',4326),f.geometry) as thedist <o:p></o:p></p>
<p class=MsoNormal>from freguesias as f <o:p></o:p></p>
<p class=MsoNormal>order by thedist <o:p></o:p></p>
<p class=MsoNormal>limit 1;<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>as you can see it returns the closest polygon to a given
point.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Problem: 4050 (**detailed**) polygons<o:p></o:p></p>
<p class=MsoNormal>exec time: 907 ms<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The Gist index was created, btw…<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Is there any way to optimize this query and avoid the
dreaded seq scan?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Txs in advance!<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Pedro Doria Meunier.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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