48 lines
1.5 KiB
Python
48 lines
1.5 KiB
Python
# The example from the paper "A read-only transaction anomaly under snapshot
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# isolation"[1].
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#
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# Here we test that serializable snapshot isolation (SERIALIZABLE) doesn't
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# suffer from the anomaly, because s2 is aborted upon detection of a cycle.
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# In this case the read only query s3 happens to be running in a parallel
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# worker.
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#
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# [1] http://www.cs.umb.edu/~poneil/ROAnom.pdf
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setup
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{
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CREATE TABLE bank_account (id TEXT PRIMARY KEY, balance DECIMAL NOT NULL);
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INSERT INTO bank_account (id, balance) VALUES ('X', 0), ('Y', 0);
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}
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teardown
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{
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DROP TABLE bank_account;
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}
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session s1
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setup { BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; }
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step s1ry { SELECT balance FROM bank_account WHERE id = 'Y'; }
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step s1wy { UPDATE bank_account SET balance = 20 WHERE id = 'Y'; }
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step s1c { COMMIT; }
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session s2
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setup { BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; }
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step s2rx { SELECT balance FROM bank_account WHERE id = 'X'; }
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step s2ry { SELECT balance FROM bank_account WHERE id = 'Y'; }
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step s2wx { UPDATE bank_account SET balance = -11 WHERE id = 'X'; }
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step s2c { COMMIT; }
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session s3
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setup {
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BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
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SET debug_parallel_query = on;
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}
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step s3r { SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id; }
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step s3c { COMMIT; }
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# without s3, s1 and s2 commit
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permutation s2rx s2ry s1ry s1wy s1c s2wx s2c s3c
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# once s3 observes the data committed by s1, a cycle is created and s2 aborts
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permutation s2rx s2ry s1ry s1wy s1c s3r s3c s2wx
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