[OSM-dev] osm2pgsql: why is osm_id not unique?

[Martijn van Oosterhout]

On Sat, Jul 19, 2008 at 6:42 PM, Sven Geggus
<lists at fuchsschwanzdomain.de> wrote:
> Hello anybody,
>
> can someone explain to me why the osm_id column generated from osm2pgsql
> is just almost but not completely unique?

Because a single feature in an OSM source file can translate into
multiple "features" in the database. Parking areas which create nodes
is the obvious one, but there are others like route-relations.

> The reason I ask, is that tools like qgis need an unique column to work,
> which I thought osm_id would be.

Then I suppose you should make a unique column...

> Can osm2pgsql be changed to make them unique? I think this would be a real
> benefit, as no additional unique id column would be needed.

I don't see how, but perhaps you have an idea?

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/