[postgis-devel] force_sfs

[Sandro Santilli]

On Fri, May 10, 2013 at 04:24:40PM +0200, Olivier Courtin wrote:
> On May 10, 2013, at 3:56 PM, Sandro Santilli wrote:

> > What's the real use of this ? Is it only for GEOS ?
> 
> Well SFCGAL retrieve SFS 1.2 geometry.
> And GEOS could only handle SFS 1.1
> 
> So when you want to nest a SFCGAL function with GEOS ones,
> it could lead to problem (for instance GEOS stop as not 
> able to deal with TRIANGLE...)
>
> First real use case of such a thing was for ST_ConcaveHull,
> when SFCGAL backend enabled, as concave hull
> mix ST_Intersection (SFCGAL), with ST_IsValid (GEOS)
> 
> > Does it need to be exposed to SQL at all ?
> 
> Yeap i think so, except if we choose to silently convert
> SFS 1.2 -> SFS 1.1 types directly before GEOS calls.
>
> > Note that we have an st_force_collection already
> > which could work for TIN and POLYHEDRALSURFACE
> > (would need to be renamed as well) so it really
> > only seems to be an issue for TRIANGLE.
> 
> Humm that's not exactly the same need,
> as with st_force_collection on a MULTIPOLYGON you will
> have a collection of POLYGON.
> (rather that with ST_ForceSFS, aim is to have pure SFS 1.1
>  geometry type)

How about ST_ForceSFS(geometry, '1.1') ?

--strk;