[OSM-dev] Ways with 40k nodes, was: osmosis pgsql schema

Stefan de Konink stefan at konink.de
Fri Oct 31 12:55:37 GMT 2008

Andy Allan wrote:
>> In case of a partial checkout you would only
>> fetch the subtrees (relations) that are in your bbox and their parent.
> The one subtree has 17M nodes, and I get the parent relation with the
> coastline tags too.

No no! bbox the subtree, so you will not get 17M nodes, but only the 
nodes in your bbox. The subtree would be only used for tagging purposes, 
and maintain parent order. This would even allow non contiguous 
subtrees, having, for example ,a specific tag over a certain amount of 

> No, hang on, that would be daft. I'd be better off making subtrees
> limited to about 1000 nodes or thereabouts, to improve the efficiency
> of partial checkouts. So then I would have sensibly sized subtrees
> (lets call them 'ways') and the master super-tree (lets call it a
> relation).

You miss the point of rewriting ways into relations. It will reduce the 
code complexity and database complexity of all operations significantly. 
The amount of tables is reduced, that means the amount of joins are 
reduced. And the indices required for database searches are now more 
efficient. Queries therefore get shorter, no need for a specific way 


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