CREATE FUNCTION generate_histogram() RETURNS TABLE (range text, freq int, bar text) AS $$
DECLARE
    bucket_id int;
    query_id int8;
BEGIN
    SELECT bucket, queryid INTO bucket_id, query_id FROM pg_stat_monitor ORDER BY calls DESC LIMIT 1;

    RETURN QUERY SELECT * FROM histogram(bucket_id, query_id) AS a (range text, freq int, bar text);
END
$$ LANGUAGE plpgsql;
CREATE FUNCTION run_pg_sleep(loops int) RETURNS void AS $$
BEGIN
    FOR i IN 1..loops LOOP
        -- 0.4 seconds step used here to hit the same histogram buckets consistently.
        -- See histogram buckets timing distribution.
	   PERFORM pg_sleep(0.4 * i);
    END LOOP;
END
$$ LANGUAGE plpgsql;
CREATE FUNCTION wait_for_new_bucket() RETURNS void AS $$
BEGIN
    -- If the bucket lifetime is less than 8 seconds, we would not fit.
    IF extract(SECOND FROM now()) > 52 THEN
        PERFORM pg_sleep(60 - extract(SECOND FROM now()));
    END IF;
END
$$ LANGUAGE plpgsql;
CREATE EXTENSION pg_stat_monitor;
SELECT wait_for_new_bucket();
 wait_for_new_bucket 
---------------------
 
(1 row)

SELECT pg_stat_monitor_reset();
 pg_stat_monitor_reset 
-----------------------
 
(1 row)

SET pg_stat_monitor.pgsm_track = 'all';
SELECT run_pg_sleep(5);
 run_pg_sleep 
--------------
 
(1 row)

SELECT substr(query, 0, 50) as query, calls, resp_calls FROM pg_stat_monitor ORDER BY query COLLATE "C";
                 query                  | calls |                  resp_calls                   
----------------------------------------+-------+-----------------------------------------------
 SELECT pg_sleep(0.4 * i)               |     5 | {0,0,0,0,0,0,0,0,0,0,0,1,1,2,1,0,0,0,0,0,0,0}
 SELECT pg_stat_monitor_reset()         |     1 | {1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
 SELECT run_pg_sleep(5)                 |     1 | {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0}
 SET pg_stat_monitor.pgsm_track = 'all' |     1 | {1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
(4 rows)

SELECT * FROM generate_histogram();
           range           | freq |              bar               
---------------------------+------+--------------------------------
 {{0.000 - 1.000}          |    0 | 
  (1.000 - 2.778}          |    0 | 
  (2.778 - 4.162}          |    0 | 
  (4.162 - 6.623}          |    0 | 
  (6.623 - 11.000}         |    0 | 
  (11.000 - 18.783}        |    0 | 
  (18.783 - 32.623}        |    0 | 
  (32.623 - 57.234}        |    0 | 
  (57.234 - 101.000}       |    0 | 
  (101.000 - 178.827}      |    0 | 
  (178.827 - 317.226}      |    0 | 
  (317.226 - 563.338}      |    1 | ■■■■■■■■■■■■■■■
  (563.338 - 1000.994}     |    1 | ■■■■■■■■■■■■■■■
  (1000.994 - 1779.268}    |    2 | ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  (1779.268 - 3163.256}    |    1 | ■■■■■■■■■■■■■■■
  (3163.256 - 5624.371}    |    0 | 
  (5624.371 - 10000.920}   |    0 | 
  (10000.920 - 17783.643}  |    0 | 
  (17783.643 - 31623.492}  |    0 | 
  (31623.492 - 56234.598}  |    0 | 
  (56234.598 - 100000.000} |    0 | 
  (100000.000 - ...}}      |    0 | 
(22 rows)

DROP EXTENSION pg_stat_monitor;