[postgis-devel] Wrong answer from new knn with recheck

Nicklas Avén nicklas.aven at jordogskog.no
Sat May 23 13:36:43 PDT 2015

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) 
(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

-------------- next part --------------
A non-text attachment was scrubbed...
Name: t.sql
Type: text/x-sql
Size: 1057 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/postgis-devel/attachments/20150523/e1837065/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: r.sql
Type: text/x-sql
Size: 148343 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/postgis-devel/attachments/20150523/e1837065/attachment-0001.bin>

More information about the postgis-devel mailing list