[postgis-devel] Snap-Rounding based overlay operations

[Darafei "Komяpa" Praliaskouski]

ср, 20 сент. 2017 г. в 17:08, Sandro Santilli <strk at kbt.io>:

> On Tue, Sep 19, 2017 at 05:18:51AM -0700, Paul Ramsey wrote:
> > I'm generally in favor of the GUC, and to some extent in favor of having
> it
> > turned on by default, though I could stand a release cycle with it off
> for
> > testing purposes. I don't think we want the granularity of declaring
> > precision by table or by feature.
>
> A GUC for enabling it and GUC for specifying a precision GRID ?
> Or letting precision GRID being figured out by GEOS internally ?
>

I am strongly against a GUC that will change precision.
We already have a switch for GEOS/CGAL backend, so a similar one for
enabling (or disabling) FIXED mode is fine.


> I generally think that precision would be a characteristic of
> a data rather than session.
>

There is a PR on validity flag for CGAL. This is a similar algorithm input
characteristic, that should be stored in geometry, if cannot be effeciently
calculated each time. And in general it can't - ST_SnapToGrid(geom, pi())
will make it a 3.14... meter grid, with all the last bits mostly set.
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