[OSM-dev] unmodified objects being uploaded?

Jon Burgess jburgess777 at googlemail.com
Sat Sep 29 11:54:05 BST 2007

On Sat, 2007-09-29 at 00:23 +0100, Richard Fairhurst wrote:
> Jon Burgess wrote:
> > Looking at the history for some objects show that they have been
> > uploaded multiple times even tough there are no obvious changes:
> > [...]
> > There are other examples in the planet diff where only the  
> > timestamp has
> > been changed on an object. This could be a sign of a bug in one of the
> > editors.
> Potlatch will upload a new way whenever a constituent part of that  
> way changes.
> So, if you move the lat/long of a node within a way, then Potlatch  
> will write a new revision of the way to the database, as well as a  
> new revision of the node.
> This isn't _quite_ as daft as it sounds. Potlatch only writes  
> "created_by" tags on ways: not nodes, not segments. In the above  
> example, you could tell that the edit was made by Potlatch because  
> the node change (no "created_by") has the same timestamp and user id  
> as a way change ("created_by=Potlatch").
> (From a Potlatch, rather than OSM db, point of view, it makes a lot  
> of sense: Potlatch's principal objects are ways and POIs; you can't  
> edit a node in Potlatch unless it's part of one or the other.)
> Is this a valid way of doing things? You could argue either way. It  
> means extra way revisions are written, but it saves significant space  
> by not adding created_by tags for the 350 nodes in a given way.

I understand that by not adding the created_by tag we save some space. 

I still do not see what Potlatch would lose if it did not upload a new
version of a node which has absolutely zero differences. From what you
mention it seems the value of this is to say that the node was part of a
way which had some other modifcations made. Is there  anything else?

This seems to mean that if a user moves a single node in a way using
Potlatch then all nodes get changed to have his user id and results in
unnecessary work for for the backend DB to rewrite all these unmodified


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