[OSM-dev] [OSM-talk] Handling of towns with different or alternative names

[Richard Fairhurst]

Stefan de Konink wrote:
> If you can agree that this tag/nds out of order thing could be the 
> main reason for these strange inserts, I am happy to help you 
> search for the source that reflects this.

I have an open mind as to what it might be.

> For some reason I think that the actual API call to update a way 
> (hence: new timestamp/user) *is* done first from a code 
> perspective, but is not finished when the request is done for 
> current tables vs history tables. If you say 'but i create an xml 
> and PUT it too' /way/<id> like anything else, then that is very 
> interesting situation and you maybe right we are looking for the 
> wrong editor.

For its transport format, Potlatch uses AMF rather than XML. Speed is vital
in an online editor, like Potlatch (or, indeed, the original applet). When
using Flash, AMF both saves bandwidth and serialisation/deserialisation
time.
http://www.jamesward.com/blog/2007/04/30/ajax-and-flex-data-loading-benchmarks/
will give you some benchmarks. (Plus, of course, it doesn't suffer from the
memory leaks that we seem to have with Ruby's XML handling.)

amf_controller.rb then takes these AMF messages, and calls exactly the same
Rails methods as the XML API does.

I would strongly recommend you look at the code that saves ways:
  
http://trac.openstreetmap.org/browser/sites/rails_port/app/controllers/amf_controller.rb#L330

FWIW, my experience is that data inconsistencies of this sort happen mostly
when the server is under very heavy load. If a process is killed halfway
through a write operation, then obviously you're going to get some sort of
inconsistency. You can order the operations so that this is less likely (cf
http://trac.openstreetmap.org/changeset/13184/), but as has been said here
extensively, this kind of stuff is always going to happen without
transactions.

Richard
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