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# The example from the paper "A read-only transaction anomaly under snapshot
# isolation"[1].
#
# Here we test that serializable snapshot isolation (SERIALIZABLE) doesn't
# suffer from the anomaly, because s2 is aborted upon detection of a cycle.
#
# [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; }
step s3r { SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id; }
step s3c { COMMIT; }
# without s3, s1 and s2 commit
permutation s2rx s2ry s1ry s1wy s1c s2wx s2c s3c
# once s3 observes the data committed by s1, a cycle is created and s2 aborts
permutation s2rx s2ry s1ry s1wy s1c s3r s3c s2wx
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