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<body>In general I think we could do a lot of cool things with aggregates.
<div>I have had a thought in my head for a very long time that I haven't had time to investigate.</div>
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<div>Quite often people is asking for a function like union in the esri world.</div>
<div>http://resources.arcgis.com/en/help/main/10.1/index.html#//000800000010000000</div>
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<div>In PostGIS we have a problem to do calculations that involves more than 2 geoemtries.</div>
<div>But as an aggregate function it vould be possible to do.</div>
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<div>/Nicklas</div>
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2014-09-01 Paul Ramsey wrote:<br />
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Only reason is nobody ever asked for it, it's hard to figure great use<br />
>cases for it.<br />
><br />
>P<br />
><br />
>On Sun, Aug 31, 2014 at 6:16 PM, Paragon Corporation
<lr@pcorp.us> wrote:<br />
>> I wasn't sure if we just thought there wasn't much utility in it or if there<br />
>> was a technical obstacle.<br />
>><br />
>> I would think that would be easier to build than the other aggregates since<br />
>> as you add more geometries it shrinks and the current aggregate state is<br />
>> always the result of the previous state plus new geometry (so no need for an<br />
>> accumulation function or a final state function) and if you ever end up with<br />
>> a geometry collection, you short-circuit out.<br />
>><br />
>> Thanks,<br />
>> Regina<br />
>><br />
>><br />
>> _______________________________________________<br />
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>> postgis-devel@lists.osgeo.org<br />
>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-devel<br />
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</lr@pcorp.us></div>
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