[OSM-dev] osm2pgsql diff mechanics

[Michael Kussmaul]

Hi,

I plan to do osm2pgsql diffs on my PostgreSQL setup. For my use-case it is important that all geometry data is valid, so after the initial import I do a cleaning of all non-valid geometry data (self-intersection, ...). 
Now my question: If I cleaned a geometry (e.g. forest) and a diff specifies a change in this geometry, what will happen? 

1.) Will the geometry completely be replaced by the new geometry as specified in the diff.
2.) Will the geometry be messed up, because the diff expects a different original geometry and now just applies a patch.
3.) Diff will fail, because it expects something different in the original geometry.
4.) ...

For my use-case 1.) would be the best, because I could then do a re-cleaning after each diff-import.

Many thanks
Michael