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

Tom Hughes tom at compton.nu
Wed Sep 16 15:30:16 BST 2009


On 16/09/09 15:17, Peter Körner wrote:

>    == Decisions ==
> The Choice that is up to be made now is between the following three
> possibilities
>    a) do not implement these calls
>    b) implement them on demand
>    c) implement them with a new column/index

[ snipped ]

>    c) this will cost disk-space and memory for the index. The CPU time
>       will be consumed only once.

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.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://www.compton.nu/




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