On Mon, 2008-08-04 at 14:51 -0700, Michal Migurski wrote:
> > Nice, works very well.
> >
> > One hiccup I see is that if I run the executable from a directory
> > other than the one where it was built, it complains that default.style
> > can't be found. Otherwise works beautifully.
>
>
> So, two frustrating things about osm2pgsql's --slim mode:
>
> I first tried doing the whole planet.osm without --slim, which worked
> well. However, when I would then use the --slim option to catch up on
> dailies, I found that a number of tables (prefix_nodes, prefix_ways,
> etc.) hadn't been created. It was not possible to do the dailies
> unless they had been planed-for from the start.
>
> The second thing is that upon going back to the original planet.osm
> with the much-slower --slim mode turned on, it required so much disk
> space that it maxed out an EC2 standard disk image.
>
> It would be nice if it were possible to do the initial planet.osm
> import without --slim for speed and space, and still import subsequent
> diffs.
I'm afraid that is not possible. The conversion from OSM to postgres is
lossy. It converts all the node references on the ways into linestring
geometries referencing the individual lat/lon of the nodes without any
reference to the IDs. This makes it impossible to update this data
without storing a copy of all the raw nodes and ways in the extra tables
generated by the slim-mode import.
An alternative way to do this is to use osmosis to update the planet
file with the daily diff and then reload this into postgres.
Unfortunately this may take too long to be a practical solution.
Another way to save more disk space is to filter out the data you don't
require. Either by applying a bounding box or by removing items from the
default.style.
Jon
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