SESSION 1                                  SESSION 2
--------------------------------           --------------------------------------
SELECT count(*) FROM test;
=> 10
                                           INSERT INTO test VALUES ('x');

SELECT count(*) FROM test;
=> 10 with read committed/serializable
=> 11 with read uncommited (dirty read)
                                           COMMIT;

SELECT count(*) FROM test;
=> 10 with serializable
=> 11 with read uncommitted/read committed