Parsed test spec with 3 sessions

starting permutation: s3_prep s2_delete s1_scan s3_parked s3_vacuum s2_freed s2_insert s2_reused s2_wakeup s1_again s3_verify
injection_points_attach
-----------------------
                       
(1 row)

step s3_prep: VACUUM (FREEZE, ANALYZE) vcr;
step s2_delete: DELETE FROM vcr WHERE k = 1;
step s1_scan: SELECT count(*) AS rows_for_key_1 FROM vcr WHERE k = 1; <waiting ...>
step s3_parked: SELECT count(*) = 1 AS parked FROM pg_stat_activity WHERE wait_event_type = 'InjectionPoint' AND wait_event = 'lion-scan-chain-entered';
parked
------
t     
(1 row)

step s3_vacuum: VACUUM vcr;
step s2_freed: 
	SELECT entries, deleted_pages > 0 AS chain_was_freed
	  FROM lion_index_stats('vcr_k');

entries|chain_was_freed
-------+---------------
      1|t              
(1 row)

step s2_insert: 
	INSERT INTO vcr SELECT i, 9 FROM generate_series(100001, 120000) i;

step s2_reused: 
	SELECT deleted_pages AS pages_left_free FROM lion_index_stats('vcr_k');

pages_left_free
---------------
              1
(1 row)

step s2_wakeup: 
	/*
	 * Detach first, so that nothing can park at the point again, then
	 * release whoever is parked now.  How MANY times the point is reached is
	 * not fixed - the two-column driver runs more than one entry scan, and a
	 * scan fires the point once per leaf it consumes an entry from -
	 * but after this step nobody is waiting on it, which is all the
	 * permutation needs.  injection_points_wakeup() searches the WAITERS, so
	 * it still works after the detach.
	 */
	SELECT injection_points_detach('lion-scan-chain-entered');
	DO $$
	DECLARE n int; zero int := 0;
	BEGIN
		FOR i IN 1 .. 6000 LOOP
			SELECT count(*) INTO n FROM pg_stat_activity
			 WHERE wait_event = 'lion-scan-chain-entered';
			IF n = 0 THEN
				zero := zero + 1;
				EXIT WHEN zero >= 10;
			ELSE
				zero := 0;
				/*
				 * The waiter clears its slot itself once it notices the
				 * counter, so it can be gone between the poll above and
				 * this call; that is a success, not a failure.
				 */
				BEGIN
					PERFORM injection_points_wakeup('lion-scan-chain-entered');
				EXCEPTION WHEN OTHERS THEN NULL;
				END;
			END IF;
			PERFORM pg_sleep(0.01);
		END LOOP;
	END $$;

injection_points_detach
-----------------------
                       
(1 row)

step s1_scan: <... completed>
rows_for_key_1
--------------
             0
(1 row)

step s1_again: SELECT count(*) AS rows_for_key_1 FROM vcr WHERE k = 1;
				  SELECT count(*) AS rows_for_key_9 FROM vcr WHERE k = 9;
rows_for_key_1
--------------
             0
(1 row)

rows_for_key_9
--------------
         20000
(1 row)

step s3_verify: SELECT lion_index_verify('vcr_k', true);
lion_index_verify
-----------------
                 
(1 row)