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Add isolation test for SERIALIZABLE READ ONLY DEFERRABLE.
This improves code coverage and lays a foundation for testing similar issues in a distributed environment. Author: Thomas Munro <thomas.munro@enterprisedb.com> Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
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‎src/test/isolation/expected/read-only-anomaly-2.out

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Parsed test spec with 3 sessions
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starting permutation: s2rx s2ry s1ry s1wy s1c s2wx s2c s3c
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step s2rx: SELECT balance FROM bank_account WHERE id = 'X';
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balance
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0
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step s2ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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step s1ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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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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step s2wx: UPDATE bank_account SET balance = -11 WHERE id = 'X';
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step s2c: COMMIT;
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step s3c: COMMIT;
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starting permutation: s2rx s2ry s1ry s1wy s1c s3r s3c s2wx
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step s2rx: SELECT balance FROM bank_account WHERE id = 'X';
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balance
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0
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step s2ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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step s1ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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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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step s3r: SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id;
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id balance
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X 0
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Y 20
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step s3c: COMMIT;
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step s2wx: UPDATE bank_account SET balance = -11 WHERE id = 'X';
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ERROR: could not serialize access due to read/write dependencies among transactions

‎src/test/isolation/expected/read-only-anomaly-3.out

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Parsed test spec with 3 sessions
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starting permutation: s2rx s2ry s1ry s1wy s1c s3r s2wx s2c s3c
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step s2rx: SELECT balance FROM bank_account WHERE id = 'X';
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balance
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0
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step s2ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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step s1ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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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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step s3r: SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id; <waiting ...>
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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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step s3r: <... completed>
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id balance
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X -11
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Y 20
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step s3c: COMMIT;

‎src/test/isolation/expected/read-only-anomaly.out

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Parsed test spec with 3 sessions
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starting permutation: s2rx s2ry s1ry s1wy s1c s3r s2wx s2c s3c
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step s2rx: SELECT balance FROM bank_account WHERE id = 'X';
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balance
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0
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step s2ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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step s1ry: SELECT balance FROM bank_account WHERE id = 'Y';
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balance
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0
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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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step s3r: SELECT id, balance FROM bank_account WHERE id IN ('X', 'Y') ORDER BY id;
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id balance
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X 0
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Y 20
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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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step s3c: COMMIT;

‎src/test/isolation/isolation_schedule

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test: read-only-anomaly
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test: read-only-anomaly-2
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test: read-only-anomaly-3
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test: read-write-unique
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test: read-write-unique-2
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test: read-write-unique-3

‎src/test/isolation/isolationtester.c

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appendPQExpBuffer(&wait_query, ",%s", backend_pids[i]);
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appendPQExpBufferStr(&wait_query, "}'::integer[]");
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/* Also detect certain wait events. */
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appendPQExpBufferStr(&wait_query,
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" OR EXISTS ("
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" SELECT * "
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" FROM pg_catalog.pg_stat_activity "
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" WHERE pid = $1 "
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" AND wait_event IN ('SafeSnapshot'))");
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res = PQprepare(conns[0], PREP_WAITING, wait_query.data, 0, NULL);
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if (PQresultStatus(res) != PGRES_COMMAND_OK)
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{

‎src/test/isolation/specs/read-only-anomaly-2.spec

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# 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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#
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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 { BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; }
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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"

‎src/test/isolation/specs/read-only-anomaly-3.spec

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# 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 can avoid the anomaly
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# without aborting any tranasctions, by instead causing s3 to be deferred
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# until a safe snapshot can be taken.
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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 { BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE; }
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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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permutation "s2rx" "s2ry" "s1ry" "s1wy" "s1c" "s3r" "s2wx" "s2c" "s3c"

‎src/test/isolation/specs/read-only-anomaly.spec

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# 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 use snapshot isolation (REPEATABLE READ), so that s3 sees a state of
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# afairs that is not consistent with any serial ordering of s1 and s2.
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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 REPEATABLE READ; }
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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 REPEATABLE READ; }
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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 { BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; }
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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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permutation "s2rx" "s2ry" "s1ry" "s1wy" "s1c" "s3r" "s2wx" "s2c" "s3c"

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