[postgis-devel] Wrong answer from new knn with recheck
pramsey at cleverelephant.ca
Sat May 23 16:57:49 PDT 2015
What happens when you run the query using the suspect house as a literal instead of doing the fun lateral query?
On May 23, 2015 at 1:36:55 PM, Nicklas Avén (nicklas.aven at jordogskog.no) wrote:
> Since I cannot reach trac I post it here.
> I have been playing some with latest trunk and latest postgresql.
> Since I cannot reach trac I cannot check that it is absolute latest
> trunk but I have r13544
> PostgreSQL I pulled from git yesterday.
> I have 2 data sets. one with roads and one with houses.
> Attached is data that reproduces the problem.
> table r is the roads and table t is the houses.
> If I then run this query:
> SELECT t.navn, r.gid, st_distance(r.geom, t.geom)
> FROM t CROSS JOIN LATERAL
> (SELECT r.gid, r.geom FROM r ORDER BY t.geom <->r.geom LIMIT 2) r;
> I get this result:
> navn | gid | st_distance
> Gramstad | 988075 | 90.2225986190226
> Gramstad | 986169 | 128.356279805393
> Sidhusgohpi | 982379 | 1379790.96016902
> Sidhusgohpi | 1724598 | 27839.424840718
> What is totally wrong here is the third row. That road is 1379 km away.
> The last row gives the right answer. The closest road to that house is
> 27 km away.
> With the full data sets I can play with the limit and see how roads from
> the first house in some way is following to the second house. road nr
> 982379 is just 215 meters away from house nr 1. So something is not
> letting go.
> Nicklas Avén
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