[OSM-dev] XML planets (was Re: New proposed directory layout for planet.openstreetmap.org)

[Roland Olbricht]

> If overall duration is an issue, is it worth patching a planet using
> hourly/minutely diffs before importing the planet itself?

Ideas are welcome, but I'm quite sure this won't help. The primary issue is 
developing time, not overall duration for this step.

For the patching itself: Reading 25 GB from disk and then writing it back 
alone will take about 800 seconds, which equals 13 minutes, for a minute diff. 
Thus, it will take for the assumed 2-16 days delay between a month and 8 
month, even if Osmosis takes no computation time at all.

Of course, you can use daily diffs instead for complete days and hour/minute 
diffs for the rest, but so you can do with Overpass API. It is just not worth 
the hassle.

Ths is what the whole story is about:

There are projects whose main concern is to process a planet file. In such a 
project, a lot of developing effort and increased system requirements are 
justified a 25% speedup.

But there are also projects where a Planet file just needs to be read, in the 
simplest possible way, because it has little impact on the project's 
performance. For those, having a fancy compression which needs some extra 
software to decompress it that may or may not work on the target platform, is 
rather a nuisance than a "developers welcome" sign.

Cheers,

Roland
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