On Mon, Dec 15, 2014 at 6:20 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Alexander Korotkov <aekorotkov@gmail.com> writes: > On Mon, Dec 15, 2014 at 4:12 PM, Heikki Linnakangas <hlinnakangas@vmware.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.