Thanks much better performance with UNION ALL -Håvard
On Sat, Oct 9, 2010 at 7:40 PM, Paragon Corporation <[email protected]> wrote: > Don't use UNION > > Try doing a UNION ALL > > UNION puts in an implicit DISTINCT which is wrong for geometries anyway > since it would just be bounding box distinct. > > Leo > http://www.postgis.us > > > ------------------------------ > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *Håvard Wahl > Kongsgård > *Sent:* Saturday, October 09, 2010 1:34 PM > *To:* [email protected] > *Subject:* [postgis-users] Slow spatial join with subquery and UNION > > SELECT COUNT(DISTINCT SPATIAL_POINTS_1.id) from SPATIAL_POINTS_1 as > SPATIAL_POINTS_1 Inner join (Select geom from SPATIAL_POINTS_2 UNION SELECT > geom from SPATIAL_POINTS_3) as SPATIAL_POINTS_X on > ST_DWithin(SPATIAL_POINTS_1.the_geom, SPATIAL_POINTS_X.geom, 500) > > This UNION subquery is very slow, there are indexes for each geom. If I > skip the UNION it's much faster. > > Is there an alternative way to do this? > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > >
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