for g in 1 2 3 4 5 6 7 8; do
for f in `perl -le 'print 0; print 2**$_ foreach 0..15'`; do
  echo JJPREFETCH $f
  pgbench -i -s 500 -n -q
  echo    'set jjfetch='$f'; 
           alter table pgbench_accounts drop constraint pgbench_accounts_pkey ; 
           delete from pgbench_accounts ; 
           vacuum verbose pgbench_accounts ;' | psql
done;
done >& jjprefetch.out;