[postgis-devel] Vive Doublebox

[Sandro Santilli]

On Wed, Dec 07, 2011 at 10:05:04AM -0800, Paul Ramsey wrote:
> On Wed, Dec 7, 2011 at 9:29 AM, Sandro Santilli <strk at keybit.net> wrote:

> > Would indices be also part of this conversion-to-double ? Implications ?
> 
> No, they would still be float, and the implications are limited.
> They'd remain the same size, the && operator would still only work on
> float boxes so it would be slightly more inclusive than if it was full
> double, and it would be possible to get "funny" results like "hey, my
> geometries are separated by <this very small distance> but && still
> returns true!". But that's not new behavior, just continuation of
> current behavior. In general our behavior would become more
> consistent.

Could you list the advantages of having a cached box based on doubles
rather than float ? So far you only mentioned avoiding the coordinate
drifts during cast-to-box, but as cast-to-box would mostly serve the
purpose of using && over it, and && being still based on float I don't
see that drift as representing any problem.

Should we list all functions dealing with boxes and expecting full
precision ? I think ST_Extent is one of them. Is that correct ?
It'd help to have a full list and for each item evaluate how important
using double precision would be.

--strk;

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