Parsed test spec with 4 sessions

starting permutation: s4b s3d s1b s2l s1q s3v s2u s1c s4c
step s4b: BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT count(*) FROM iso_bd;
count
-----
 3000
(1 row)

step s3d: DELETE FROM iso_bd WHERE id % 4 = 0;
step s1b: BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT count(*) FROM iso_bd;
count
-----
 2250
(1 row)

step s2l: SELECT pg_advisory_lock(20983, 1);
pg_advisory_lock
----------------
                
(1 row)

step s1q: SELECT iso_bd_q(true); <waiting ...>
step s3v: VACUUM iso_bd;
step s2u: SELECT pg_advisory_unlock(20983, 1);
pg_advisory_unlock
------------------
t                 
(1 row)

step s1q: <... completed>
iso_bd_q
--------
agree   
(1 row)

step s1c: COMMIT;
step s4c: COMMIT;