Parsed test spec with 3 sessions

starting permutation: snap3 b1 grant1 vac2 snap3 c1 cmp3
step snap3: 
	INSERT INTO frozen_witness
	SELECT datfrozenxid FROM pg_database WHERE datname = current_catalog;

step b1: BEGIN;
step grant1: 
	GRANT TEMP ON DATABASE isolation_regression TO regress_temp_grantee;

step vac2: VACUUM (FREEZE); <waiting ...>
step snap3: 
	INSERT INTO frozen_witness
	SELECT datfrozenxid FROM pg_database WHERE datname = current_catalog;

step c1: COMMIT;
step vac2: <... completed>
step cmp3: 
	SELECT 'datfrozenxid retreated'
	FROM pg_database
	WHERE datname = current_catalog
		AND age(datfrozenxid) > (SELECT min(age(x)) FROM frozen_witness);

?column?
--------
(0 rows)