[postgis-tickets] [PostGIS] #2354: ST_Union performance problem

[PostGIS]

#2354: ST_Union performance problem
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 Reporter:  akrherz      |       Owner:  pramsey
     Type:  enhancement  |      Status:  new    
 Priority:  medium       |   Milestone:         
Component:  postgis      |     Version:  1.5.X  
 Keywords:               |  
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 I use ST_Union to join together National Weather Service forecast zones
 and counties.  This has worked fine for me for many years now.  The most
 recent update of these zones by the NWS must include a few higher
 resolution geometries that now cause ST_Union to peg CPU for a few minutes
 before returning a result.  My environment is:

      PostgreSQL 9.1.9 on x86_64-unknown-linux-gnu, compiled by gcc (GCC)
 4.4.7 20120313 (Red Hat 4.4.7-3), 64-bit POSTGIS="1.5.8"
 GEOS="3.3.8-CAPI-1.7.8" PROJ="Rel.4.7.1, 23 September 2009" LIBXML="2.7.6"
 USE_STATS (procs from 1.5 r7360 need u
 pgrade)

 I am attaching my reproducer table dump, which I dumped via the command:

     pg_dump -Fc -t postgis_union_issue postgis > st_union_problem.dump

 the simple command to reproduce

     select st_union(geom) from postgis_union_issue;

 ST_IsValid indicates all the geometries are valid.

 Thanks

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2354>
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