Parsed test spec with 2 sessions starting permutation: modify vac stats step modify: insert into smalltbl select max(id)+1 from smalltbl; step vac: vacuum smalltbl; step stats: select relpages, reltuples from pg_class where oid='smalltbl'::regclass; relpages reltuples 1 21 starting permutation: modify open fetch1 vac close stats step modify: insert into smalltbl select max(id)+1 from smalltbl; step open: begin; declare c1 cursor for select 1 as dummy from smalltbl; step fetch1: fetch next from c1; dummy 1 step vac: vacuum smalltbl; step close: commit; step stats: select relpages, reltuples from pg_class where oid='smalltbl'::regclass; relpages reltuples 1 20 starting permutation: modify vac stats step modify: insert into smalltbl select max(id)+1 from smalltbl; step vac: vacuum smalltbl; step stats: select relpages, reltuples from pg_class where oid='smalltbl'::regclass; relpages reltuples 1 21