Thanks Regina. For some reason ST_Collect doesn't give exactly the same result. For example I'm trying to merge european countries in one shape and with ST_Collects it omits England and other islands while ST_Union includes them. Anyway, my union finished after 4 hours. I'm joining two tables on an ST_Intersect, one of which has ~15000 features (polygons) and the other just one (a complex polygon). The query's been running for two hours... I hope I'll see the end of it before the end of the day! (I've set the indexes where I could and tuned PostgreSQL)
Regards. On Mon, Aug 4, 2008 at 12:25 PM, Obe, Regina <[EMAIL PROTECTED]>wrote: > Try the trick documented here > > http://postgis.refractions.net/documentation/manual-svn/ST_Collect.html > > On hindsight - I realized the ST_Multi call here is probably unnecessary so > you can leave that part out. > > Hope that helps, > Regina > > > > ------------------------------ > *From:* [EMAIL PROTECTED] [mailto: > [EMAIL PROTECTED] *On Behalf Of *danny > *Sent:* Monday, August 04, 2008 5:04 AM > > *To:* PostGIS Users Discussion > *Subject:* Re: [postgis-users] Merge all polygons from a dataset > > 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 <[EMAIL PROTECTED]> 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 < >> [EMAIL PROTECTED]> 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 >>> >>> [EMAIL PROTECTED] >>> >>> 804-698-4405 >>> >>> Open Source Modeling Tools: >>> >>> http://sourceforge.net/projects/npsource/ >>> >>> -----Original Message----- >>> *From:* [EMAIL PROTECTED] [mailto: >>> [EMAIL PROTECTED] *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 <[EMAIL PROTECTED]> >>> 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:* [EMAIL PROTECTED] [mailto: >>> [EMAIL PROTECTED] *On Behalf Of *danny >>> *Sent:* Friday, August 01, 2008 6:12 AM >>> *To:* [email protected] >>> *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 >>> ------------------------------ >>> >>> *The substance of this message, including any attachments, may be >>> confidential, legally privileged and/or exempt from disclosure pursuant to >>> Massachusetts law. It is intended solely for the addressee. If you received >>> this in error, please contact the sender and delete the material from any >>> computer. * >>> ------------------------------ >>> >>> *Help make the earth a greener place. If at all possible resist printing >>> this email and join us in saving paper. * >>> >>> >>> _______________________________________________ >>> postgis-users mailing list >>> [email protected] >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>> >>> >>> >>> _______________________________________________ >>> postgis-users mailing list >>> [email protected] >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>> >>> >> > ------------------------------ > > * The substance of this message, including any attachments, may be > confidential, legally privileged and/or exempt from disclosure pursuant to > Massachusetts law. It is intended solely for the addressee. If you received > this in error, please contact the sender and delete the material from any > computer. * > > ------------------------------ > > * Help make the earth a greener place. 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