[postgis-users] Merge all polygons from a dataset

[danny]

I'm getting very long processing time from ST_Union (on a shape of europe at
1/100000 it's been running since 2 hours and hasn't finished yet; on my
previous one of 1/1000000 it took ~1 hour)
Any other alternative and quicker ways to accomplish the same operation?
I just executed st_buffer(st_collect(the_geom)) but still waiting. Should it
take as long? ST_Collect by itself executes fast but it's result violates
the geometry check constraint.



On Fri, Aug 1, 2008 at 5:31 PM, danny <whatevar89 at gmail.com> wrote:

> Thanks Robert.
>
> I actually exported from ogr2ogr and it created a shape that worked fine in
> ArcView.
>
> Best
>
>
>
>
> On Fri, Aug 1, 2008 at 5:19 PM, Burgholzer,Robert <
> rwburgholzer at deq.virginia.gov> wrote:
>
>>  Could ArcView perhaps want some columns other than just the shape?
>> Perhaps you could put a numeric ID or something else in there.
>>
>>
>>
>> Just a thought,
>>
>>
>>
>> Robert W. Burgholzer
>>
>> Surface Water Modeler
>>
>> Office of Water Supply and Planning
>>
>> Virginia Department of Environmental Quality
>>
>> rwburgholzer at deq.virginia.gov
>>
>> 804-698-4405
>>
>> Open Source Modeling Tools:
>>
>> http://sourceforge.net/projects/npsource/
>>
>> -----Original Message-----
>> *From:* postgis-users-bounces at postgis.refractions.net [mailto:
>> postgis-users-bounces at postgis.refractions.net] *On Behalf Of *danny
>> *Sent:* Friday, August 01, 2008 9:30 AM
>> *To:* PostGIS Users Discussion
>> *Subject:* Re: [postgis-users] Merge all polygons from a dataset
>>
>>
>>
>> Many thanks, Regina! Indeed ST_Union generated the polygon, invisible in
>> PgAdmin!!
>>
>> It creates a nice layer when I open it in uDig.
>>
>> However when I export it with pgsql2shp, the shape is unreadable by
>> ArcView with the errmsg: Number of shapes does not match the number of table
>> records.
>>
>> Here's how I created the layer:
>>
>> create table europe_contour();
>> SELECT addgeometrycolumn('db, 'europe_contour', 'the_geom',
>> 32767,'MULTIPOLYGON', 2 );
>> insert into europe_contour(the_geom) values( (select st_union(the_geom)
>> from europe));
>>
>> Then I generate the shapefile:
>>
>> "c:\Program Files\PostgreSQL\8.3\bin\pgsql2shp.exe" -u postgres -P
>> password -f europe_contour db europe_contour
>>
>> Any suggestions perhaps on anything I've wrong?
>>
>>  On Fri, Aug 1, 2008 at 1:15 PM, Obe, Regina <robe.dnd at cityofboston.gov>
>> wrote:
>>
>> Erik,
>>
>> How were you using ST_Union and what exactly do you mean by no result.  no
>> result as it looks blank?  If you are using something like PgAdmin III - it
>> will look blank because it exceeds the buffer supported by PgAdmin III.
>>
>>
>>
>> SELECT the_geom is null
>>
>> FROM (somequery or table) as foo
>>
>> LIMIT 1
>>
>>
>>
>> will tell you if its actually returning no geometry
>>
>>
>>
>> Hope that helps,
>>
>> Regina
>>
>>
>>  ------------------------------
>>
>> *From:* postgis-users-bounces at postgis.refractions.net [mailto:
>> postgis-users-bounces at postgis.refractions.net] *On Behalf Of *danny
>> *Sent:* Friday, August 01, 2008 6:12 AM
>> *To:* postgis-users at postgis.refractions.net
>> *Subject:* [postgis-users] Merge all polygons from a dataset
>>
>> Hello everybody,
>>
>> I've converted a shapefile of Europe to PostGIS. I would like to merge all
>> the countries together so that I only have one polygon left, the whole
>> contour of Europe. I have tried ST_Union that gives me no result. I've tried
>> several other functions to no avail. Does anybody know how I should proceed?
>>
>> Many thanks,
>>
>> Erik
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