# The example from the paper "A read-only transaction anomaly under snapshot
# isolation"[1].
#
# Here we test that serializable snapshot isolation can avoid the anomaly
# without aborting any transactions, by instead causing s3 to be deferred
# until a safe snapshot can be taken.
#
# [1] http://www.cs.umb.edu/~poneil/ROAnom.pdf

setup
{
	CREATE TABLE bank_account (id TEXT PRIMARY KEY, balance DECIMAL NOT NULL);
	INSERT INTO bank_account (id, balance) VALUES ('X', 0), ('Y', 0);
}

teardown
{
	DROP TABLE bank_account;
}

session s1
setup 		{ BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; }
step s1ry	{ SELECT balance FROM bank_account WHERE id = 'Y'; }
step s1wy	{ UPDATE bank_account SET balance = 20 WHERE id = 'Y'; }
step s1c 	{ COMMIT; }

session s2
setup		{ BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; }
step s2rx	{ SELECT balance FROM bank_account WHERE id = 'X'; }
step s2ry	{ SELECT balance FROM bank_account WHERE id = 'Y'; }
step s2wx	{ UPDATE bank_account SET balance = -11 WHERE id = 'X'; }
step s2c	{ COMMIT; }

session s3
setup		{ BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE; }
step s3r	{ SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id; }
step s3c	{ COMMIT; }

permutation s2rx s2ry s1ry s1wy s1c s3r s2wx s2c s3c