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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">OK, so after making the changes suggested by Tommaso the query runs almost 50% faster! Here’s the new query<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">WITH RECURSIVE flow(gid, geom) AS (<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE ST_DWithin(e.geom,f.geom, 0.01) AND f.gid=15<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> UNION ALL<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> SELECT n.gid, n.geom<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> FROM electric_line n, flow f<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> WHERE ST_Distance(ST_EndPoint(f.geom),ST_StartPoint(n.geom)) <= 0.01<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">SELECT *, ST_ASGeoJSON(ST_Transform(geom,4326),6) AS geojson<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">FROM flow;<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">R</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">émi-C, I am trying to make a walk through from the fuse down to the
last electric line. The performance is great when less than 400 linestrings. </span>
<span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">On resources, the sever currently runs with 2 CPUs and 6GB of ram. I could add more CPU and memory if you think it will make a difference. Also, I’m running on pgsql 9.2 and POSTGIS
2.0.1 r9979<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">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Jon<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"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> postgis-users-bounces@lists.osgeo.org [mailto:postgis-users-bounces@lists.osgeo.org]
<b>On Behalf Of </b>Rémi Cura<br>
<b>Sent:</b> Tuesday, December 10, 2013 5:21 AM<br>
<b>To:</b> PostGIS Users Discussion<br>
<b>Subject:</b> Re: [postgis-users] functions<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On a more high level: <o:p></o:p></p>
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<p class="MsoNormal">I'm guessing you are using the recursive cte to walk trough a graph.<o:p></o:p></p>
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<p class="MsoNormal">There are ways to accelerate this, but at the cost of increase of memory usage and duplication of data.<o:p></o:p></p>
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<p class="MsoNormal">It depends a lot on you graph properties (has it a lots of nodes, connectivity, centralness, etc)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">(of course you have an index on "gid" or it is a primary key (implicit index) ).<br>
<br>
If perf is really an issue, you could turn to more specialize grpah db (look for spar-ql)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Cheers,<o:p></o:p></p>
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<p class="MsoNormal">Rémi-C<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">2013/12/10 tommaso <<a href="mailto:tommasodb@googlemail.com" target="_blank">tommasodb@googlemail.com</a>><o:p></o:p></p>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
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<p class="MsoNormal">Why do you do ST_AsText(e.geom)::geometry? This is equivalent to e.geom. Change the query so:<br>
SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE ST_DWithin(e.geom, f.geom 0.01) AND f.gid=$1 .....<br>
<br>
No sure if it does help, but you you can also try so:<br>
SELECT e.gid, e.geom FROM electric_line e JOIN fuses f ON ST_DWithin(e.geom, f.geom, 0.01) WHERE f.gid=$1<br>
<br>
Also<br>
WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)<br>
can be changed to:<br>
WHERE ST_Distance(ST_EndPoint(f.geom),ST_StartPoint(n.geom)) <= 0.01<br>
which should be faster.<br>
<br>
Obviously you need a GIST index on booth geometry columns.<br>
<br>
If it all does not help please attach some test data.<br>
<br>
Cheers, Tommaso<o:p></o:p></p>
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<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal">On 12/10/2013 03:01 AM, Jonatan Malaver wrote:<o:p></o:p></p>
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<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">Another question, what can I do to improve performance on the query? The query can take 2 seconds or more.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><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"">
<a href="mailto:postgis-users-bounces@lists.osgeo.org" target="_blank">postgis-users-bounces@lists.osgeo.org</a> [<a href="mailto:postgis-users-bounces@lists.osgeo.org" target="_blank">mailto:postgis-users-bounces@lists.osgeo.org</a>]
<b>On Behalf Of </b>Jonatan Malaver<br>
<b>Sent:</b> Monday, December 09, 2013 8:52 PM<br>
<b>To:</b> PostGIS Users Discussion<br>
<b>Subject:</b> Re: [postgis-users] functions</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">Thank you!!!</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">Jon</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
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<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><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"">
<a href="mailto:postgis-users-bounces@lists.osgeo.org" target="_blank">postgis-users-bounces@lists.osgeo.org</a> [<a href="mailto:postgis-users-bounces@lists.osgeo.org" target="_blank">mailto:postgis-users-bounces@lists.osgeo.org</a>]
<b>On Behalf Of </b>tommaso<br>
<b>Sent:</b> Monday, December 09, 2013 12:57 PM<br>
<b>To:</b> PostGIS Users Discussion<br>
<b>Subject:</b> Re: [postgis-users] functions</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">This should work:<br>
<br>
create or replace function flow(integer) RETURNS TABLE (gid int, geom geometry, geojson text) AS<br>
$$ <br>
<br>
WITH RECURSIVE flow(gid, geom) AS (<br>
<br>
SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE ST_DWithin(ST_AsText(e.geom)::geometry, ST_AsText(f.geom)::geometry, 0.01) AND f.gid=$1<br>
<br>
UNION ALL<br>
<br>
SELECT n.gid, n.geom<br>
<br>
FROM electric_line n, flow f<br>
<br>
WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)<br>
<br>
)<br>
<br>
SELECT *, ST_ASGeoJSON(ST_Transform(geom,4326),6) AS geojson<br>
<br>
FROM flow;<br>
<br>
$$<br>
LANGUAGE SQL;<br>
<br>
<br>
SELECT * FROM flow(1);<br>
<br>
<br>
On 12/09/2013 03:57 PM, Jonatan Malaver wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> I’m new to postgis/postgresql. I was wondering if anyone could tell me how to make a function out of this sql query:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">WITH RECURSIVE flow(gid, geom) AS (<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE ST_DWithin(ST_AsText(e.geom)::geometry, ST_AsText(f.geom)::geometry, 0.01) AND f.gid=' . $_GET['fuse'] . '<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> UNION ALL<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> SELECT n.gid, n.geom<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> FROM electric_line n, flow f<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> )<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">SELECT *, ST_ASGeoJSON(ST_Transform(geom,4326),6) AS geojson<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">FROM flow;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> I’d like to make a function flow(gid)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Jon<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:12.0pt"><o:p> </o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>postgis-users mailing list<o:p></o:p></pre>
<pre><a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a href="http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users" target="_blank">http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users</a><o:p></o:p></pre>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>postgis-users mailing list<o:p></o:p></pre>
<pre><a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a href="http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users" target="_blank">http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users</a><o:p></o:p></pre>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><br>
_______________________________________________<br>
postgis-users mailing list<br>
<a href="mailto:postgis-users@lists.osgeo.org">postgis-users@lists.osgeo.org</a><br>
<a href="http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users" target="_blank">http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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