[OSM-dev] [API] Suggestion: Baselines

Shaun McDonald shaun at shaunmcdonald.me.uk
Wed May 27 09:49:26 BST 2009


On 26 May 2009, at 13:47, Chris Browet wrote:

>
>
> 2009/5/26 Stefan de Konink <stefan at konink.de>
> Chris Browet wrote:
>    If you just want to materialise the entire database at a certain
>    interval, don't you think this will grow very fast?
>
>
> I don't know. A baseline would only consist of a list of all objects  
> id with their associated version number at a certain point in time,  
> not the actual objects...
>
> Think of a way X; it consist of n nodes. If you take the this way at  
> changeset Y, you would still have to find all nodes positions at  
> time(Y).
>
> Sure, but as we'd take a version snapshot of all objects anyway, the  
> X way will still be only say 8 bytes for the id and n (don't know  
> the definaition for versions, let's assume 4) bytes for the version.  
> That is 12 bytes per object * 360.000.000 is ~4.5Gb.
>
> Assuming daily, one year rotating, online baselines, that makes 1.5  
> Tb, i.e. 2 big disks (with overhead), i.e. 200€.
>
> Not that expensive IMHO...

I think that you are looking for something that Matt has talked about  
a few times, and that is a global version number like svn.

Shaun

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