Hi, Yes, thanks Jamie, that is indeed what I meant. Didn't proofread the message well enough!
Regards, Loretta ----- Original Message ----- From: James DeMichele <[email protected]> Date: Friday, September 10, 2010 6:50 pm Subject: Re: [postgis-users] ST_Union vs ST_Collect > Hello, Loretta, when you said: " replacing the ST_DUMP with > ST_COLLECT...", did you mean that you replaced the ST_UNION with > ST_COLLECT? > > -Jamie > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of L > Bogert-O'Brien > Sent: Friday, September 10, 2010 3:26 PM > To: [email protected] > Subject: [postgis-users] ST_Union vs ST_Collect > > The question: > Why would CT_COLLECT work when CT_UNION does not? > > The background: > There are 49 distinct CMAs in my y2006.ca_ct.cbf_clp table. Each of > them have many multipolygons within them that touch each other by > boundaries only. I wanted to create a table containing a single > dissolved multipolygon for each CMA, so I created the following query > to insert the data into the new table, y2006.ca_cma_cbf_clp: > > INSERT INTO y2006.ca_cma_cbf_clp (pruid, cmauid, the_geom_4269) > (SELECT dmp.pruid, dmp.cmauid, > ST_MULTI(ST_BUFFER(ST_UNION(dmp.dmp_geom), 0.0)) > FROM (SELECT pruid, cmauid, > > cleangeometry(ST_BUFFER((ST_DUMP(the_geom_4269)).geom,0.0)) AS > dmp_geom FROM y2006.ca_ct_cbf_clp) AS dmp --9683 rows > of dumped > geometries > GROUP BY pruid, cmauid > ORDER BY pruid, cmauid); --49 rows of CMAs > > This returned 49 rows, but there were two of them that had geometries > that were NULL, and the following errors were seen: > > NOTICE: TopologyException: found non-noded intersection between > -79.4565 44.2272, -79.4565 44.2272 and -79.4565 44.2272, -79.4565 > 44.2272 -79.4565 44.2272 > NOTICE: TopologyException: Directed Edge visited twice during > ring-building -123.035 49.3916 > (These locations were within the two geometries that were missing.) > > So I just made one change, replacing the ST_DUMP with ST_COLLECT, and > then I got the results I was expecting. There were no errors and all > 49 entries in the new table had valid geometries. > > Thanks for any clarification you can give on the difference between > ST_UNION and ST_COLLECT and when one should be used over the other. > > Regards, > > Loretta > > > _______________________________________________ > 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 > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
