[osmosis-dev] Osmosis use case

[Frederik Ramm]

Hi,

Walschlager, Gerard wrote:
> I appreciate your quick response!  I am not surprised by your answer.
> Any idea on how much disk space would be required by a PostGIS
> database that would hold the entire planet.osm file data?

I think it would be between 100 and 150 GB for either schema; but only 
30 GB if you do option 2 (osm2pgsql) in non-slim mode. In non-slim mode, 
osm2pgsql needs more RAM (at least 16 GB during import) but produces a 
smaller, and non-updatable, database.

> I'm not sure what the "simple schema" is.  I assume that is different
> than resolution #2 that you indicated in your reply?  

Yes, osmosis and osm2pgsql use different schemas. Osmosis supports the 
APIDB schema and the "Simple" schema while osm2pgsql has its own schema, 
available in "slim" and "non-slim" varieties.

 From a data modeling perspective - and I'm on somewhat thin ice here, 
happy for anyone to chip in and confirm or protest - the APIDB schema is 
the most powerful because it has all the data plus history. The "Simple" 
schema, as well as the Osm2pgsql slim-mode schema, still have a full OSM 
data snapshot (and you could theoretically convert from one to the 
other, or from APIDB into one of them) but they don't have history. The 
non-slim osm2pgsql schema, lastly, carries only a processed selection of 
OSM data (exactly what is needed for the map - nothing more). You could 
theoretically convert from any of the others to non-slim osm2pgsql, but 
never in the other direction.

> I assume that
> in answer #2, there is a standard schema that Mapnik assumes must be
> in place in the database it will query and that schema is different
> than the "simple schema" specified in answer #1?

Yes. To me more precise, Mapnik itself can be made to work with any 
schema, even the "Osmosis simple" schema, but the schema created by 
osm2pgsql and the style sheet commonly used in OSM work together and if 
you were to use Mapnik with the Osmosis simple schema you'd have to 
write your own style sheet.

Bye
Frederik