Query to create statistics

statsQuery.sql

/*  example usage
select * from statsQuery( 10,3,
 'pgr_drivingDistance(', 
 'select id, source, target, cost, reverse_cost from eu_2po_4pgr where id <> 1',
 ', 1 , 0.005 , false, true)'
 );

select * from statsQuery(10,3, 'pgr_dijkstra(',
 'select id, source, target, cost, reverse_cost from eu_2po_4pgr
     where id <> 1 ',
 ', 1, 2007168, false, false)');

*/



create or replace function statsQuery(m integer, n integer, pg_fn text, subsql text, restFn text) 
returns TABLE (
   seq    INTEGER,
   sql    text,
   lim   integer,
   avgt   float,
   err text) AS

$body$
DECLARE
  time1 time;
  time2 time;
  sumt float;
  deltaTime time;
    info record;
BEGIN
  lim := 1;
  seq := 0;
  FOR i in 1 .. 5  
  LOOP
    seq := seq + 1;
    sql := 'select * from ' ||pg_fn|| quote_literal(' select * from (' || subsql || ' limit ' || lim || ' ) as _b' ) ||restFn;
    sumt := 0;
    FOR j in 1 .. n
    LOOP
      
      RAISE NOTICE 'Running test %, % with limit % ', seq, j, lim;
      time1 := clock_timestamp();
      
      BEGIN
      execute sql into info;
      EXCEPTION WHEN OTHERS THEN
        err = SQLERRM;
      END;
      time2 := clock_timestamp();
      deltaTime := time2-time1;
      sumt = sumt + extract(epoch from deltaTime);
    END LOOP;
    avgt := sumt/n;
    return next;
    lim = lim * 10;
  END LOOP;

 FOR i in 1 .. (m-5)
  LOOP
    seq := seq + 1;
    sql := 'select * from ' ||pg_fn|| quote_literal(' select * from (' || subsql || ' limit ' || lim || ' ) as _b' ) ||restFn;
    sumt :=0;
    FOR j in 1 .. n
    LOOP
      RAISE NOTICE 'Running test %, % with limit % ', seq, j, lim;
      
      time1 := clock_timestamp();
      
      BEGIN
      execute sql into info;
      EXCEPTION WHEN OTHERS THEN
        err = SQLERRM;
      END;
      time2 := clock_timestamp();
      deltaTime := time2-time1;
      sumt = sumt + extract(epoch from deltaTime);
    END LOOP;
    avgt := sumt/n;
    
    return next;
    lim = lim + 100000;
  END LOOP;
  
END
$body$
language plpgsql volatile strict   cost 100 rows 100;