On Mon, Dec 15, 2014 at 6:20 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > Alexander Korotkov <aekorot...@gmail.com> writes: > > On Mon, Dec 15, 2014 at 4:12 PM, Heikki Linnakangas < > hlinnakan...@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. ------ With best regards, Alexander Korotkov.
