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?
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