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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi
</span><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">again</span><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"><o:p> </o:p></span></p>
<p class="MsoNormal">I tried this first:<o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US">CREATE TABLE public."Areas_union" AS select (st_dump(st_union("the_geom"))).geom from "Areas";<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It took 168 sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Then I tried this:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">CREATE TABLE public." Areas_union " AS select (ST_dump(ST_Buffer(St_Collect(the_geom), 0))).geom as "the_geom" from " Areas";<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">And it took 46 sec.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Is there any problems doing so, the result looked ok?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Kind regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><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"">Från:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Malm, Paul (Operations AIM)
<br>
<b>Skickat:</b> den 3 mars 2020 07:29<br>
<b>Till:</b> PostGIS Users Discussion<br>
<b>Ämne:</b> SV: [postgis-users] st_union<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks Paul and Alexande!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">/Paul<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Från:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> postgis-users [mailto:postgis-users-bounces@lists.osgeo.org]
<b>För </b>Alexandre Neto<br>
<b>Skickat:</b> den 3 mars 2020 01:53<br>
<b>Till:</b> PostGIS Users Discussion<br>
<b>Ämne:</b> Re: [postgis-users] st_union<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Uhmmm... So, if there's no join or where clause, the index is not used at all?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Somehow, I thought that internally ST_union would still use it to decide which geometries need be merged together in the same part.<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 clarifying.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Alexandre Neto<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">A segunda, 2/03/2020, 22:02, Paul Ramsey <<a href="mailto:pramsey@cleverelephant.ca">pramsey@cleverelephant.ca</a>> escreveu:<o:p></o:p></p>
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<p class="MsoNormal">On Mon, Mar 2, 2020 at 1:16 PM Alexandre Neto <<a href="mailto:senhor.neto@gmail.com" target="_blank">senhor.neto@gmail.com</a>> wrote:<br>
><br>
> Stating the obvious,<br>
><br>
> Do you have a spatial index on your geom column?<br>
<br>
That will make no difference, the query is reading the whole contents<br>
of the column, a spatial index will do nothing.<br>
<br>
P<br>
<br>
<br>
><br>
> Alexandre Neto<br>
><br>
> A segunda, 2/03/2020, 17:04, Paul Ramsey <<a href="mailto:pramsey@cleverelephant.ca" target="_blank">pramsey@cleverelephant.ca</a>> escreveu:<br>
>><br>
>> No, if it’s returning the answer you want, that’s the way to do it, and there’s no way around it.<br>
>><br>
>> > On Mar 2, 2020, at 6:25 AM, <<a href="mailto:paul.malm@lfv.se" target="_blank">paul.malm@lfv.se</a>> <<a href="mailto:paul.malm@lfv.se" target="_blank">paul.malm@lfv.se</a>> wrote:<br>
>> ><br>
>> > Hi list,<br>
>> > I would like to do this:<br>
>> > CREATE TABLE public."Areas_union" AS select (st_dump(st_union("the_geom"))).geom from "Areas";<br>
>> ><br>
>> > But it takes such a long time to execute, is there a smarter way to do it?<br>
>> ><br>
>> > Kind regards,<br>
>> > Paul<br>
>> > _______________________________________________<br>
>> > postgis-users mailing list<br>
>> > <a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><br>
>> > <a href="https://lists.osgeo.org/mailman/listinfo/postgis-users" target="_blank">
https://lists.osgeo.org/mailman/listinfo/postgis-users</a><br>
>><br>
>> _______________________________________________<br>
>> postgis-users mailing list<br>
>> <a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><br>
>> <a href="https://lists.osgeo.org/mailman/listinfo/postgis-users" target="_blank">
https://lists.osgeo.org/mailman/listinfo/postgis-users</a><br>
><br>
> _______________________________________________<br>
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