CREATE EXTENSION pg_qualstats;
-- Make sure sure we'll see at least one qual
SET pg_qualstats.sample_rate = 1;
CREATE TABLE pgqs AS SELECT id FROM generate_series(1, 100) id;
SELECT COUNT(*) FROM pgqs WHERE id = 1;
 count 
-------
     1
(1 row)

SELECT lrelid::regclass::text, lattnum, occurences, execution_count,
    nbfiltered, constvalue, eval_type
FROM pg_qualstats;
 lrelid | lattnum | occurences | execution_count | nbfiltered | constvalue | eval_type 
--------+---------+------------+-----------------+------------+------------+-----------
 pgqs   |       1 |          1 |             100 |         99 | 1::integer | f
(1 row)

SELECT COUNT(*) > 0 FROM pg_qualstats;
 ?column? 
----------
 t
(1 row)

SELECT COUNT(*) > 0 FROM pg_qualstats();
 ?column? 
----------
 t
(1 row)

SELECT COUNT(*) > 0 FROM pg_qualstats_example_queries();
 ?column? 
----------
 t
(1 row)

SELECT pg_qualstats_reset();
 pg_qualstats_reset 
--------------------
 
(1 row)

SELECT COUNT(*) FROM pg_qualstats();
 count 
-------
     0
(1 row)