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); 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)