<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered medium)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Verdana;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:Arial;
color:windowtext;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I was wondering if there is a good (or best practice)
approach on how to merge geometry features that are touching or overlapping and
have one common value in one table field.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Here is what I was trying to do: given a large dataset such
as the (detailed NHD data layer) of rivers in California I created multiple
buffers and inserted the results into a new table with one geometry column adding
a score value to each of the same buffers distances used. Thus the buffer
polygon layer has a score with a value of 10,100,500 and 1000 m corresponding
to the buffer distance used. Given the approach I used to create the
buffers those are often spatially overlapping (because there was no merge operation
of the buffers and because the rivers are split along the flow line in multiple
segments by node in the source shape file). The resulting layer works ok for my
purposes (which is to retrieve information in which buffers a certain location
is intersecting it with the river buffer (results can be 10,100,500 and 1000 or
no intersect with the buffers).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Now the layers is about 20 GB big disk size having a lot of unnecessary
geometries with are overlapping.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>How can I go about merging all the existing geometries on
this huge data set into a result layer that has (optimally ) only 4 polygons
with the result scores to find my intersects. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>When I tried some of my own approaches (e.g. using st_collect
and such to do this) so far whenever I started these sever resource intensive
operations soon these where aborted by the system because i got some kind of
out of memeonry errosr on my server (an ubuntu achjien). Is there a good way to
optimize this kind of query operation without using 100% of my server ram so
that I will not run out of memory or resulting in a lengthy query that would be
running for 6 weeks or so </span></font><font size=2 face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings'>J</span></font><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'> ?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Any query examples or general insight are greatly
appreciated .<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Cheers<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Karsten<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Verdana><span lang=DE
style='font-size:12.0pt;font-family:Verdana;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Verdana><span lang=DE
style='font-size:12.0pt;font-family:Verdana;color:navy'>Karsten Vennemann</span></font><span
lang=DE><o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=DE
style='font-size:12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span lang=DE
style='font-size:10.0pt;font-family:Verdana;color:navy'>Terra GIS Ltd</span></font><span
lang=DE><o:p></o:p></span></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span lang=DE
style='font-size:10.0pt;font-family:Verdana;color:navy'>2119 Boyer Ave E</span></font><span
lang=DE><o:p></o:p></span></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:navy'>Seattle, WA 98112</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:navy'>USA</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:navy'>tel ++ 206 905 1711</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=navy face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:navy'>fax ++ 925 905 1711</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
</body>
</html>