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

On 12/15/2014 05:22 PM, Alexander Korotkov wrote:

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.

Right. I don't think point <-> polygon is too useful by itself, but we need an example in core that could make use KNN-GiST recheck patch. We can't write a regression test for it otherwise, for starters.

Actually, we probably could've used the circle <-> polygon for that just as well...