Re: Commit fest 2014-12, let's begin!

On Mon, Dec 15, 2014 at 6:20 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Alexander Korotkov <aekorotkov(at)gmail(dot)com> writes:
> > On Mon, Dec 15, 2014 at 4:12 PM, Heikki Linnakangas <
> hlinnakangas(at)vmware(dot)com
> >> wrote:
> >> Right. I also looked at it briefly, but I wasn't sure if we really want
> >> it. AFAICT, no-one has actually asked for that operator, it was written
> >> only to be an example of an operator that would benefit from the
> knn-gist
> >> with recheck patch.
>
> > Lack of recheck is major limitation of KNN-GiST now. People are not
> asking
> > for that because they don't know what is needed to implement exact KNN
> for
> > PostGIS. Now they have to invent kluges like this:
> > [ query using ORDER BY ST_Distance ]
>
> It's not apparent to me that the proposed operator is a replacement for
> ST_Distance. The underlying data in an example like this won't be either
> points or polygons, it'll be PostGIS datatypes.
>
> In short, I believe that PostGIS could use what you're talking about,
> but I agree with Heikki's objection that nobody has asked for this
> particular operator.
>

"polygon <-> point" is for sure not ST_Distance replacement. I was giving
this argument about KNN-GiST with recheck itself. "polygon <-> point" is
needed just as in-core example of KNN-GiST with recheck.

------
With best regards,
Alexander Korotkov.