Question

i am writing a folloing pgsql procedure :

CREATE OR REPLACE FUNCTION KNN(gid_ integer)
RETURNS Text AS $body$
DECLARE
row_ RECORD;
BEGIN
    SELECT  g1.gid As SOURCE, g2.gid As Neighbors  FROM polygons as g1, polygons as   g2  WHERE g1.gid = $1 and g1.gid <> g2.gid  ORDER BY g1.gid, 
ST_Distance(g1.the_geom,g2.the_geom) limit 5;
END
$body$
LANGUAGE plpgsql;

Now that the query return 5 rows for each value of arrgument supplied to procedure. How can i return those 5 rows. Also, how can i execute the procedure for all values of argument stored in a table polygons as column gid. Please somebody give the full code please. thankful to you.

Answer 1

You can use the RETURNS TABLE syntax to implicitly create OUT variables:

CREATE OR REPLACE FUNCTION KNN(
    gid_ integer
) RETURNS TABLE (
    source  integer,
    neighbor integer
) LANGUAGE SQL AS $$
    SELECT g1.gid As SOURCE
         , g2.gid As Neighbors
      FROM polygons AS g1,
           polygons AS g2
     WHERE g1.gid = $1
       AND g1.gid <> g2.gid
     ORDER BY g1.gid
         , ST_Distance(g1.the_geom,g2.the_geom)
     LIMIT 5;
$$;

To use it, use SELECT * FROM KNN(42) and you will get back up to five two-column rows.