[OSM-dev] [OSM-talk] Abstract on getting historic information about usage of a node

Peter Körner osm-lists at mazdermind.de
Wed Sep 16 19:41:19 BST 2009



Ian Dees schrieb:
> On Wed, Sep 16, 2009 at 9:30 AM, Tom Hughes <tom at compton.nu 
> <mailto:tom at compton.nu>> wrote:
> 
> 
>     This is NOT true. As I explained yesterday there is a very good reason
>     why we do not store a node revision in current_way_nodes and way_nodes.
> 
>     The problem is that if you do that then every time a node is changed you
>     have to go and find every way which uses that node and update it to use
>     the new version of the node. So it costs CPU time every time a node
>     is changed.
> 
> 
> Can a way assume that it uses the most recent version of a node until 
> the way is changed? Then, when a way's revision number increments, all 
> of the rev#'s for the nodes that make up that way are saved along with 
> the way's history.
But this wouldn't solve the problem of "give me all ways that used node 
#50, v3" as the last time way #10 was updated it only used node #50, v1 
and so that's the last information that's saved.

Peter




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