create or replace procedure tps() as $$
declare
  v1 int8;
  v2 int8;
begin
  select txid_snapshot_xmax(txid_current_snapshot()) into v1;
  commit;
  perform pg_sleep(1);
  select txid_snapshot_xmax(txid_current_snapshot()) into v2;
  commit;
  raise notice 'tps: %', v2-v1;
end;
$$ language plpgsql ;