On Thu, Mar 15, 2012 at 12:56:38PM -0400, Pierre Racine wrote:
> >  1. find out intersecting pairs into cache (id1,id2,geom1,geom2)  2. update 
> > cache
> > set geom1 = st_difference(geom1, geom2)  3. update main set geom = c.geom1
> > from cache where id1 = id
> 
> Hum... Life is never that easy.
> 
> That would work if one polygon would always overlap with only one polygon but 
> if one polygon is overlapped by two polygons or more the same polygon as two 
> differences associated with it in the second step and only the last one will 
> remains in the last update...

True, should be an iterative process until "cache" becomes empty.

--strk;

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