[postgis-devel] [PostGIS] #1828: Estimate returned by geography_gist_selectivity results in slow query plan for ST_DWithin

[PostGIS]

#1828: Estimate returned by geography_gist_selectivity results in slow query plan
for ST_DWithin
---------------------------+------------------------------------------------
 Reporter:  realityexists  |       Owner:  pramsey      
     Type:  defect         |      Status:  new          
 Priority:  medium         |   Milestone:  PostGIS 2.0.1
Component:  postgis        |     Version:  2.0.x        
 Keywords:                 |  
---------------------------+------------------------------------------------

Comment(by pramsey):

 Removing the RESTRICT and JOIN causes the planner to fall back to the
 default selectivity estimate which is basically "yeah, it's really
 selective!" in all cases. Which turns out to be good for your particular
 query, less good for others. The problem is that somewhere, somehow our
 estimator is underestimating the selectivity of your particular query
 parameters, either because the estimate calculations are wrong or perhaps
 because the stats gathered or wrong or perhaps because of something
 special/interesting about your geometries themselves.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1828#comment:3>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.