[OSM-talk] Naga City in OSM Re: GML to OSM

[Andy Allan]

On Thu, Apr 10, 2008 at 12:52 PM, Lester Caine <lester at lsces.co.uk> wrote:

>  But that only addresses one small 'problem' and misses the bigger one of
>  finding 'all the golf courses in England' or 'all the Islands in the
>  Philippines'. A single lookup to find ALL the boundaries you are currently
>  looking within is probably not a major overhead, but the reverse search is
>  going to involve potentially hundreds of thousands of such enquiries?

No, you're completely wrong about "hundreds of thousands" of queries.
"All the golf courses in England" is fairly trivial for the database
to calculate when there is an index on the leisure column (so it's
lightning to get all the leisure=golf_course polygons) and then
selecting those that are in the "England" polygon (using the spatial
indexes to compare the bounding boxes of the polygons). It's what
indexes are for - there's very little processing involved.

Honestly, it's much simpler and much faster than you think.

Cheers,
Andy