[Geocoding] Bbox option on Nominatim

[Rodolphe Quiédeville]

Sarah Hoffmann <lonvia at denofr.de> writes:

> Hi,
>
> On Wed, Jan 15, 2014 at 03:31:04PM +0100, Rodolphe Quiédeville wrote:
>> So if I write here it's because I maintain a nominatim serveur for
>> geocoding on a bbox that covers Europe, so I loaded it with an export
>> from geofabrik (thanks to them) and now run hourly update on it. If I
>> well understood, the update process load worlwide datas in the database,
>> so I propose to add an option --bbox to Nominatim to filter the
>> changes. The option will have the same structure as osm2pgsql and the
>> value will be set on osm2pgsql command line using it's option '-b'.
>> 
>> Before doing the patch, I wanted to discuss it about you, what do you
>> think about and have you some hints ?

Hi Sarah,

Thanks a lot for your answer.

> There is no general objection to adding such a parameter but you should
> be aware that the bbox option in osm2pgsql might actually do less than what 
> you want. It only filters node objects, ways and relations are still imported
> completely. Most of the time, this will do what you want because without
> nodes outside the bbox, the geometry for the ways and relations cannot be
> computed and without a geometry, the objects should not appear in the
> Nominatim tables. However, osm2pgsql's slim tables will still grow with
> the unnecessary data.

Thanks to precise this point on osm2pgsl, even if we'll still have
unecessary data we'll have less than doing nothing.

> If daily updates are sufficient for you, you should try Geofabrik's
> daily diffs[1]. They work well with Nominatim and will avoid the 
> problem of bloated tables. The setup is described in the installation
> instructions.

I didn't know this process, it's good to know it. Our bounding bow is a
little larger than europe, we way soon integrate some of north african
countries, so it will be easy for use to use a larger bbox, even if it's
not perfect we'll won't import datas from 2 contient, it's the first
step.

I'll prepare a path, and do a PR when ready. I'll also open a ticket on
Trac to inform other on my work.

Best regards

-- 
Rodolphe Quiédeville
Expert Tsung - Consulting en performance des SI
Tel : 06 13 79 63 41
http://blog.rodolphe.quiedeville.org