init.sql

DROP TABLE simple;
CREATE TABLE simple (
	val int
);

-- After this run t1 and t2 in two different sessions, executing the SQL statements
-- in the order given by the commands after them.
--
-- Notice how t2 aborts with the error below, even so it should be serializable with t1.
--
-- ERROR:  could not serialize access due to read/write dependencies among transactions
-- DETAIL:  Reason code: Canceled on identification as a pivot, during commit attempt.
-- HINT:  The transaction might succeed if retried.

t1.sql

BEGIN ISOLATION LEVEL SERIALIZABLE; -- 1
INSERT INTO simple (val) VALUES (1); -- 3
SELECT * FROM simple WHERE val = 3; -- 5
COMMIT; --7

t2.sql

BEGIN ISOLATION LEVEL SERIALIZABLE; -- 2
INSERT INTO simple (val) VALUES (2); -- 4
SELECT * FROM simple WHERE val = 4; -- 6
COMMIT; --8