<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:garamond,new york,times,serif;font-size:12pt">okay so I plotted those points that were in the topology exception error, and narrowed it down to two adjacent polygons. So now I have:<br>select st_union(st_buffer(the_geom,0.1)) from base.current_assessment_parcel where gid in (36,37)<br>(returns the topology exception)<br><br>Checking out those two parcels, they seem legit in qgis / arcview. (no weird nodes that I can see). <br><br>Attached is the output from the following query: select gid, st_asewkt(the_geom) from base.current_assessment_parcel where gid in (36,37) <br>I'm relatively newbie to postgis, so can't see what might be causing this, if someone could look at this for me?<br><div> </div>unfortunately, I am on vacation starting tonight, and won't be available to provide further details. If the answer is "your polygons are just
messed up" then so be it. These are from someone elses shapefile. Just want to help if this is indeed a bug.<br><br>Thanks for your help Kevin.<br>Lee.<br><div><br></div><div style="font-family: garamond,new york,times,serif; font-size: 12pt;"><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Kevin Neufeld <kneufeld@refractions.net><br><b><span style="font-weight: bold;">To:</span></b> PostGIS Users Discussion <postgis-users@postgis.refractions.net><br><b><span style="font-weight: bold;">Sent:</span></b> Tue, September 14, 2010 10:49:25 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [postgis-users] unioning a buffer - bug?<br></font><br>
Interesting. Something sure sounds amiss. Are the results null? Is
there anything usual occurring at the TopologyException location? Is
your dataset large? Can you winnow it down to the few polygons that
might be causing the problem (this may be just the polygons around the
TopologyException location)? If so, you could paste the representation
of the geometries in PasteBin or something so we can help you isolate
the problem.<br>
<br>
Also, what version of GEOS do you have installed?<br>
SELECT PostGIS_Full_Version();<br>
<br>
Cheers,<br>
Kevin<br>
<br>
On 9/14/2010 6:03 AM, Lee wrote:
<blockquote type="cite">
<div style="font-family: garamond,new york,times,serif; font-size: 12pt;">Hi
Kevin,<br>
<br>
I assumed I have no results because when I load one of the working
queries as a view (eg. select st_buffer(the_geom,0.1)) in QGIS, or in
ArcGIS, I see all my results as I would expect, but when I modify the
query to st_union(st_buffer()), all my parcels disappear and I have a
blank canvas.<br>
<br>
Also, with st_isvalid(st_union(st_buffer(the_geom,0.1))) returning null
(neither t nor f) I guess I just assumed. Anyways, results for your
suggestions are inline, below. <br>
<br>
<div style="font-family: garamond,new york,times,serif; font-size: 12pt;">Thanks
for your help. Any further ideas?<br>
<br>
Lee.<br>
<div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2">
<hr size="1"><b><span style="font-weight: bold;">From:</span></b>
Kevin Neufeld <a rel="nofollow" class="moz-txt-link-rfc2396E" ymailto="mailto:kneufeld@refractions.net" target="_blank" href="mailto:kneufeld@refractions.net"><kneufeld@refractions.net></a><br>
<b><span style="font-weight: bold;">To:</span></b>
<a rel="nofollow" class="moz-txt-link-abbreviated" ymailto="mailto:postgis-users@postgis.refractions.net" target="_blank" href="mailto:postgis-users@postgis.refractions.net">postgis-users@postgis.refractions.net</a><br>
<b><span style="font-weight: bold;">Sent:</span></b> Tue, September
14, 2010 12:12:46 AM<br>
<b><span style="font-weight: bold;">Subject:</span></b> Re:
[postgis-users] unioning a buffer - bug?<br>
</font><br>
How are you determining you have no results? <br>
<br>
Try:<br>
<tt>CREATE TABLE results AS<br>
SELECT st_union(st_buffer(the_geom,0.1)) as the_geom <br>
FROM base.current_assessment_parcel;<br>
<br>
<span style="font-weight: bold; color: rgb(127, 0, 63);">NOTICE:
TopologyException: found non-noded intersection between 586714
4.95189e+006, 586714 4.95189e+006 and 586714 4.95189e+006, 586739
4.9519e+006 586714 4.95189e+006</span><br style="font-weight: bold; color: rgb(127, 0, 63);">
<span style="font-weight: bold; color: rgb(127, 0, 63);">Query
returned successfully with no result in 1078 ms.</span><br>
<br>
<br>
<br>
SELECT count(*) FROM results;<br>
<br>
<span style="font-weight: bold; color: rgb(127, 0, 63);">1</span><br>
<br>
SELECT ST_Summary(the_geom) FROM results;</tt><br>
<br>
<span style="color: rgb(127, 0, 63);">This returns blank.</span><br>
<br>
<span style="font-family: monospace;"><br>
(snip)<br>
</span><tt></tt><br>
-- Kevin<br>
<br>
On 9/13/2010 7:07 AM, Lee wrote:
<blockquote type="cite">
<div style="font-family: garamond,new york,times,serif; font-size: 10pt; color: rgb(3, 61, 33);"><font size="3"><span style="font-weight: bold;">So after some googling I see
similar problems, but no solutions posted.</span><br style="font-weight: bold;">
<br style="font-weight: bold;">
<span style="font-weight: bold;">I am trying to union a buffer, but
the query is returning no results. Here is ultimately what I would
like to achieve:</span></font><br>
<br>
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0); font-weight: bold;">select
st_union(st_buffer(the_geom,0.1))
as the_geom from
base.current_assessment_parcel</span><br>
<br>
<font size="3"><span style="font-weight: bold;">Here are some
troubleshooting steps I have taken to try narrow it down:</span></font><br>
<br style="color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">select
st_isvalid(the_geom)
a from base.current_assessment_parcel group by a</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">TRUE</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">select
st_isvalid(st_buffer(the_geom,0.1))
a from
base.current_assessment_parcel group by a</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">TRUE</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">select
st_isvalid(st_union(the_geom))
from base.current_assessment_parcel</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">TRUE</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">select
st_isvalid(st_union(st_buffer(the_geom,0.1)))
from
base.current_assessment_parcel</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">NOTICE:
TopologyException:
found non-noded intersection between 586714
4.95189e+006, 586714 4.95189e+006 and 586714 4.95189e+006, 586739
4.9519e+006 586714 4.95189e+006</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">Total
query
runtime: 859 ms.</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">
<span style="font-family: Courier New,courier,monaco,monospace,sans-serif; color: rgb(0, 0, 0);">1
row
retrieved.</span><br style="font-family: Courier New,courier,monaco,monospace,sans-serif;">
<font size="3"><span style="font-weight: bold;">(returns blank
record)</span></font><br>
<br style="font-family: garamond,new york,times,serif;">
<div style="font-family: Courier New,courier,monaco,monospace,sans-serif;"><font size="3"><span style="font-family: garamond,new york,times,serif; font-weight: bold;"> And
just
for fun</span></font><br>
<span style="color: rgb(0, 0, 0);">select
st_isvalid(st_buffer(st_union(the_geom),0.1)) a from
base.current_assessment_parcel</span><br style="color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0);">TRUE</span><br style="color: rgb(0, 0, 0);">
</div>
<font size="3"><br style="font-family: Courier New,courier,monaco,monospace,sans-serif; font-weight: bold;">
</font>
<div><font size="3"><span style="font-weight: bold;">I guess my
next
step would be to try the snap to grid functions, but the first query
above should work, shouldn't it?</span><br style="font-weight: bold;">
<br style="font-weight: bold;">
<span style="font-weight: bold;">Any help appreciated. Thanks.</span><br style="font-weight: bold;">
<span style="font-weight: bold;">Lee</span></font><br>
</div>
</div>
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