[OSM-dev] Too many slow queries in db
tom at compton.nu
Tue Sep 4 11:55:47 BST 2007
In message <46DD35ED.4080308 at frankieandshadow.com>
David Earl <david at frankieandshadow.com> wrote:
> On 04/09/2007 11:21, Tom Hughes wrote:
>> The slow queries will essentially all be along the lines of:
>> SELECT ... FROM current_nodes
>> WHERE latitude BETWEEN ... AND ...
>> AND longitude BETWEEN ... AND ...
> The way I addressed this problem in the name finder was to create a
> "region number". Each region is about 111km square: 1 degree of latitude
> and gradually decreasing amounts of longitude away from the equator.
> The number of each region is 1000 * lat + f(lon), so given a lat,lon it
> is easy to get the region number. It is also easy to compute the
> neighbouring region numbers.
That's essentially what the quadtile idea does, but regions are
effectively nested so that range of region numbers is actually a
bigger region so you can choose how big or small a region to read.
Tom Hughes (tom at compton.nu)
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