[postgis-users] Re: looking for some perf data

[Stephen Davies]

Many years ago, I tried to implement a fairly simple GIS application 
using separate B-trees on lat/long coordinates.

The idea died as soon as the data volumes became non-trivial.

The reason was obvious in hindsight: a query for x>=g1 and x <=g2 and 
y>=t1 and y<=t2 using separate B-trees has to retrieve a "vertical" and 
then a "horizontal" slice of the whole world and then take the 
intersect. 

R-trees, quad-trees etc greatly reduce this cost.

HTH,
Stephen Davies
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