K-Nearest Neighbor Query in PostGIS

Question

I am using the following Nearest Neighbor Query in PostGIS :

SELECT g1.gid g2.gid FROM points as g1, polygons g2   
WHERE g1.gid <> g2.gid
ORDER BY g1.         


        

Answer 1

You can do it with KNN index and lateral join.

SELECT v.gid, v2.gid,st_distance(v.the_geom, v2.the_geom)
  FROM geonames v, 
       lateral(select * 
                 from geonames v2
                where v2.id<>v.id
                ORDER BY v.the_geom <-> v2.the_geom LIMIT 10) v2
where v.gid in (...) - or other filtering condition