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.
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