On Dec 20, 2011, at 7:44 PM, Brian Stempin wrote: > I've been out of the loop for a bit, but try this: > > SELECT Count(c_id) > FROM c, continents n > WHERE c.the_geom && n.the_geom AND > ST_Intersects(c.the_geom, n.the_geom) AND > n.continent = 'North America'; > > The key line being: > c.the_geom && n.the_geom >
If you see the EXPLAIN QUERY PLAN I posted (see below), ST_Intersects automatically does an && check. Nevertheless, I tried your specific suggestion above, and it took 201 seconds. No joy. > Check out item 7.7: > http://postgis.refractions.net/documentation/manual-1.5/reference.html > > The && uses the bounding boxes to check if they overlap. This is a very > quick operation that might eliminate the need to further examine if two > geoms are intersecting. > > HTH, > Brian > > On Tue, Dec 20, 2011 at 8:28 PM, Puneet Kishor <punk.k...@gmail.com> wrote: > >> >> On Dec 20, 2011, at 7:21 PM, Paul Ramsey wrote: >> >>> Chop up the continents into smaller pieces. >>> >> >> >> hmmm... I am not sure I understand the above. And then what? UNION each >> smaller piece query? >> >> >>> On Tue, Dec 20, 2011 at 4:35 PM, Puneet Kishor <punk.k...@gmail.com> >> wrote: >>>> This is probably a really basic question... my ST_Within or >> ST_Intersects selecting points in a continent are way too slow (both take >> upward of 200 secs). >>>> >>>> SELECT Count(c_id) >>>> FROM c, continents n >>>> WHERE ST_Intersects(c.the_geom, n.the_geom) AND >>>> n.continent = 'North America'; >>>> >>>> >>>> Both tables have gist indexes on the geometries. The above query has >> the following plan >>>> >>>> "Aggregate (cost=9.66..9.67 rows=1 width=4)" >>>> " -> Nested Loop (cost=0.00..9.66 rows=1 width=4)" >>>> " Join Filter: _st_intersects(c.the_geom, n.the_geom)" >>>> " -> Seq Scan on continents n (cost=0.00..1.10 rows=1 >> width=32)" >>>> " Filter: ((continent)::text = 'North America'::text)" >>>> " -> Index Scan using pbdb__collections_the_geom on collections >> c (cost=0.00..8.30 rows=1 width=104)" >>>> " Index Cond: (c.the_geom && n.the_geom)" >>>> >>>> The table c has approx 120K rows, and the continents table has 8 >> rows.Suggestions on how I can improve this? Yes, the computer is otherwise >> very swift and modern. >>>> >>>> >>>> >>>> -- >>>> Puneet Kishor >> _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
