[postgis-devel] GBOXF

[Sandro Santilli]

On Tue, Nov 29, 2011 at 03:24:59PM +0000, Mark Cave-Ayland wrote:
> On 29/11/11 15:10, Sandro Santilli wrote:
> >  Mark Cave-Ayland wrote:

> >>My feeling is that if we use floats then we minimise the usefulness
> >>of the cache because it reduces the number of use cases that it
> >>could be used to optimise (and I'm fairly sure that some functions
> >>will assume that the second predicate in the paragraph above is
> >>true, and therefore give wrong answers in certain cases).
> >
> >Would be useful to have a few of these use cases listed here.
> >The only one I can think about would be using&&  to really check
> >for equality of points.
> 
> Another case to think about would be GROUP BY, which works by
> performing an equality comparison between bounding boxes - again,
> two very similar yet distinct geometries could be considered equal.

This is also true for two very different geometries yet having
the same bounding box, so doesn't seem a good example to me.
Ie:

 LINESTRING(0 0, 10 0, 10 10)
 LINESTRING(0 0, 10 10)

I guess you were referring once again only to points ?

--strk;

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