On 12/15/2014 03:45 PM, Alexander Korotkov wrote:
On Mon, Dec 15, 2014 at 4:12 PM, Heikki Linnakangas <hlinnakan...@vmware.com
wrote:
On 12/15/2014 08:37 AM, Michael Paquier wrote:
On Mon, Dec 15, 2014 at 3:09 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
Michael Paquier <michael.paqu...@gmail.com> writes:
- Point to polygon distance operator
I looked at that briefly during the last fest, but was unsure whether it
was too entangled with the GiST patches that Heikki was looking at.
Recalling my memories of this morning, things are rather independent.
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. If there is some other, real, use for the knn-gist with
recheck patch, then I'm OK with that, but otherwise it's dubious to add an
operator just so that it can then be made faster by another patch. That
said, it seems quite harmless, so might as well commit it.
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:
WITH closest_candidates AS (
SELECT
streets.gid,
streets.name,
streets.geom
FROM
nyc_streets streets
ORDER BY
streets.geom <->
'SRID=26918;POINT(583571.905921312 4506714.34119218)'::geometry
LIMIT 100
)
SELECT gid, name
FROM closest_candidates
ORDER BY
ST_Distance(
geom,
'SRID=26918;POINT(583571.905921312 4506714.34119218)'::geometry
)
LIMIT 1;
See blog posts:
http://blog.light42.com/wordpress/?p=102
http://workshops.boundlessgeo.com/postgis-intro/knn.html
Ugh. Ok, sold :-). I'll review...
- Heikki
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