[OSM-talk] Mapnik has busstops

[Martin Spott]

Hi Robert,

"Robert (Jamie) Munro" wrote:

> [...] Schuler is working on what I
> think will be the answer to all our problems - migrating the current
> database structure to PostGIS without changing it, and then adding
> spatial columns with triggers.
> 
> These spatial columns are not part of the logical model of the data,
> which remains unchanged, they are just added as a sort of index or
> cache.

Well, there are well known methods to render pre-processed data for
example in data-wareheouse applications during night. This allows users
to run statistics on the data the next day during office hours while
significantly cutting down the processing time of these individual
statistics.

The current case with OSM is a bit different: There's an unambiguous
way for two-way transformation of OSM's lat/lon numbers into WKT
representation of an OGC-style database - what you call "spatial
columns". This means the basic data model can remain unchanged and
you'll still profit from the WKT representation - including the
indexing that is attached to it. Only small adjustment to the SELECT
and INSERT/UPDATE statemens buys you a big advantage here without being
exposed to the risk of redundant data storage.

Cheerio,
	Martin.
-- 
 Unix _IS_ user friendly - it's just selective about who its friends are !
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