Christopher Condit <con...@sdsc.edu> wrote: > > I have two tables that are georeferenced (although in this case I'm not using > PostGIS) that I need to join. > A ( lat | lon | depth | value) > |A| = 1,100,000 > > B ( lat | lon | attributes) > |B| = 14,000,000 > > A is a special case because the lat / lon values are all at half degree > intervals (ie 33.5, -12.5). The lat/lons in B are arbitrary. > I've written a function in B called getSpecialLat(latitude) and > getSpecialLon(longitude) to calculate the correct A latitude and built an > index on both functions. > > Here's the query that I'm trying, but it's rather slow: > SELECT B.* FROM B, > (SELECT lat, lon FROM A WHERE value > 0 AND value < 2 AND depth = 0) AS foo > WHERE getSpecialLat(B.lat) = foo.lat AND getSpecialLon(B.lon) = foo.lon > > "Nested Loop (cost=3569.88..32055.02 rows=1414 width=422)" > " -> Index Scan using A_valueidx on A (cost=0.00..555.26 rows=6 width=16)" > " Index Cond: ((value > 0) AND (value < 2))" > " Filter: (depth = 0)" > " -> Bitmap Heap Scan on B (cost=3569.88..5029.48 rows=424 width=422)" > " Recheck Cond: ((getSpecialLon((B.lon)::numeric) = A.lon) AND > (getSpecialLat((B.lat)::numeric) = A.lat))" > " -> BitmapAnd (cost=3569.88..3569.88 rows=424 width=0)" > " -> Bitmap Index Scan on Blonidx (cost=0.00..1760.38 > rows=84859 width=0)" > " Index Cond: (getSpecialLon((B.lon)::numeric) = A.lon)" > " -> Bitmap Index Scan on Blatidx (cost=0.00..1766.81 > rows=84859 width=0)" > " Index Cond: (getSpeicalLat((B.latitude)::numeric) = > A.lat)" > > Am I missing something in terms of speeding up this query?
I'd be interested to see if the query rewritten as a JOIN would be faster. -- Bill Moran http://www.potentialtech.com -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
