[OSM-dev] New, faster, planet dump tool

Brett Henderson brett at bretth.com
Tue Sep 25 14:27:23 BST 2007

Jon Burgess wrote:
> Yes, it is possible in theory to do incremental updates, so long as
> the  PostgreSQL database has the details on all nodes, segments and
> ways. As you mention, the '--slim' modes does store all this
> information and it should be possible to apply the diff on top of this
> and work out which geometry entries need to be updated.
> Historically the RAM code has been so much faster than the DB backed
> that even applying a weeks worth of updates would probably be slower
> than reloading the whole thing. If the updates were very small
> near-real time changes then it could probably be done much faster.
> There are quite a few complications to implement this in practice so
> it would probably take me some time to get the possible glitches
> resolved.
I have no doubt it's harder than it sounds :-)  I have enough trouble 
replicating osm changes into an identical mysql schema ...  It's 
interesting that for large changesets that it may be quicker to reload.  
While I knew change application is slower, I didn't realise to what extent.

It looks like we'll have daily diffs available in the near future.  
While they're probably not useful for mapnik purposes at this point they 
might be useful for testing against.  spaetz has written a nice launch 
script for creating change files using osmosis that will allow any 
replication intervals to be established if they're successful.


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