2008/9/21 Anton Belyaev <anton.belyaev@xxxxxxxxx>: > Hello, > > I am implementing a map application. There are towns with altitude, > longitude and population. > One of the tasks is to be able to query N biggest (by population) > towns within a rectangle. > > Something like (maybe the syntax in not quite right, but the idea is obvious): > SELECT * FROM towns where alt1 <= alt <= alt2 AND long1 <= long <= > long2 ORDER BY population LIMIT 10; > > If I create an R-tree index on coordinates (alt, long) this will speed > up the query significantly. But it is still far from optimal: Despite > we need only 10 biggest towns, all towns in the rectangle specified > will be examined. > > What if we include population into R-tree index? This index will > handle a 3D space with coordinates (alt, long, population). > Will this 3D index perform better than that 2D index? > > In fact, I lack some details on how Postges handles ORDER_BY and LIMIT > inside R-tree indexes. > Extensive answers and links are appreciated. > > Thanks. > Anton. > Sorry, I meant latitude (lat) instead of altitude (alt).
