[gdal-dev] 'Polygons as multipolygons' option for OSM driver

[Even Rouault]

> The behaviour of the driver would be that no simple polygons (polygons that
> are described as ways) would be reported until the file has been
> completely processed.
> 
> The algorithm would be something like that :
> - store ways in the temporary way DB as currently, but don't advertize ways
> that are identified as area for now
> - when examining relations, when a polygon described as a way has been
> "consumed" as being the outer way of a relation, it will be removed from
> the temporary way DB (actually, probably just tagged as being no longer
> advertizable, in case it would be needed by another relation afterwards) -
> at the end, report all ways that are areas that remain in the temporary
> way DB as being advertizable

I've implemented the above in r24774. It might have an impact of performance 
(not benchmarked, and hopefully not too big) and if you turn -progress, it 
will seem to be stuck at 100% for longer as before, since there is now the 
post processing of closed ways that are not referenced by relations to do.

Best regards,

Even