[OSM-dev] Tiled download of larger areas from the api

[Christopher Schmidt]

On Sat, Jun 14, 2008 at 11:21:59AM +0100, Andy Robinson (blackadder-lists) wrote:
> bvh wrote:
> >Sent: 13 June 2008 4:26 PM
> >To: dev at openstreetmap.org
> >Subject: [OSM-dev] Tiled download of larger areas from the api
> >
> >Timo Schlussler proposed a patch to merkaartor to work around the
> >API limit on the download area. It basically divides the area in
> >chunks acceptable for the api and downloads them one by one.
> >
> >Are there any objections from the server side of things to include
> >this?
> 
> I'd have thought that rather defeats the object of the current API
> restriction.

The current API restriction is designed to prevent requesting huge
datasets in a single request, because the memory that they use causes
the number of processes that can be run to be limited.

This is exactly the kind of thing that t at h does: if an area is too large
(too many nodes) then it splits the data up into 10 'slices' and
requests those slices instead.

Given that, I think this fits in line with the way that existing tools
handle requesting data that is too large for API limits... however, if
poorly implemented, it could be a real pain in the butt. If someone
requests -180,-90,180,90, you'd end up with thousands of requests sent
by the client to the server, and that would be problematic... 

Regards,
-- 
Christopher Schmidt
MetaCarta