[postgis-devel] [PostGIS] #1828: Estimate returned by geography_gist_selectivity results in slow query plan for ST_DWithin
PostGIS
trac at osgeo.org
Tue Jul 3 09:55:59 PDT 2012
#1828: Estimate returned by geography_gist_selectivity results in slow query plan
for ST_DWithin
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Reporter: realityexists | Owner: mcayland
Type: defect | Status: new
Priority: medium | Milestone: PostGIS 2.0.2
Component: postgis | Version: 2.0.x
Keywords: |
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Comment(by pramsey):
The problem is that for <const> && <const> we're returning
DEFAULT_SELECTIVITY, which is very high. So the <const> && <const> term is
washing out the other one, the one we care about. As the comment in the
code block notes, the <const> && <const> case should return either 0 or 1,
depending on the actual evaluation of the statement, but not something in
between. I'm wondering if returning 1 might actually be the path of "less
harm" in a temporary hack, rather than returning DEFAULT_SELECTIVITY.
--
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1828#comment:36>
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