[postgis-devel] Fixed precision for ST_Intersection, ST_Union, etc.

[Daniel Baston]

My rationale here is that it's not the job of ST_Intersection to clean up
its inputs before computing the intersection, much like the current overlay
functions don't call ST_MakeValid on their inputs.  I think there is a
place for a ST_ReducePrecision / ST_SnapToGrid that reduces precision and
cleans up collapsed geometries, etc., but I don't think it's something that
should be automatically run on the inputs of all overlay functions.

Dan

On Sun, Mar 13, 2016 at 4:42 AM, Sandro Santilli <strk at keybit.net> wrote:

> On Thu, Mar 10, 2016 at 07:47:49AM -0500, Daniel Baston wrote:
> > You're right, I didn't describe that well.  I should say instead that
> these
> > functions aren't using GEOS' behavior of cleaning up topological
> collapses
> > (GEOS_PREC_NO_TOPO and GEOS_PREC_KEEP_COLLAPSED in the CAPI).  GEOS is
> > indeed doing a pointwise precision reduction, which should be a no-op in
> my
> > use case but may not be in others.
>
> What's the rationale for NOT handling the collapsing ?
> Theoretically, feeding invalid geometries to GEOS overlay operations
> should result in an exception being thrown or some other undesired
> result, so why taking the risk at all ?
>
> --strk;
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