f1166c0421
Previously, the view contents could become inconsistent with the base tables in the following scenarios: 1) A concurrent transaction modifies a base table and commits before the incremental view maintenance starts in the current transaction. 2) A concurrent transaction modifies a base table and commits before the create_immv or refresh_immv command generates data. 3) Concurrent transactions incrementally update a view with a self-join or modify multiple base tables simultaneously. Incremental updates of a view are generally performed sequentially using an exclusive lock. However, even if we are able to acquire the lock, a concurrent transaction may have already incrementally updated the view and been committed before we can acquire it. In REPEATABLE READ or SERIALIZABLE isolation levels, this could lead to an inconsistent view state, which is the cause of the first issue. To fix this, a new field, lastivmupdate, has been added to the pg_ivm_immv catalog to record the transaction ID of the most recent update to the view. Before performing view maintenance, the transaction ID is checked. If the transaction was still in progress at the start of the current transaction, an error is raised to prevent anomalies. To fix the second issue, the timing of CreateTrigger() has been moved to before data generation. This ensures that locks conflicting with table modifications have been acquired on all base tables. In addition, the latest snapshot is used in READ COMMITTED level during the data generation to reflect committed changes from concurrent transactions. Additionally, inconsistencies that cannot be avoided through locking are prevented by checking the transaction ID of the last view update, as done for the first issue. However, concurrent table modifications and create_immv execution still cannot be detected at the time of view creation. Therefore, create_immv raises a warning in REPEATABLE READ or SERIALIZABLE isolation levels, suggesting that the command be used in READ COMMITTED mode or that refresh_immv be executed afterward to ensure the view remains consistent. The third issue was caused by the snapshot used for checking tuple visibility in the table's pre-update state not being the latest one. To fix this, the latest snapshot is now used in READ COMMITTED mode. Isolation tests are also added. Issue #104
46 lines
1.5 KiB
Python
46 lines
1.5 KiB
Python
# Test interaction between concurrent transactions performing
|
|
# refresh_immv and insert in REPEATABLE READ isolation level
|
|
|
|
setup
|
|
{
|
|
CREATE TABLE a (i int);
|
|
INSERT INTO a VALUES (1);
|
|
SELECT pgivm.create_immv('mv(x,y)', 'SELECT * FROM a a1, a a2 WHERE a1.i = a2.i');
|
|
CREATE VIEW v(x,y) AS SELECT * FROM a AS a1, a AS a2 WHERE a1.i = a2.i;
|
|
CREATE FUNCTION check_mv() RETURNS text AS
|
|
$$ SELECT CASE WHEN count(*) = 0 THEN 'ok' ELSE 'ng' END
|
|
FROM ((SELECT * FROM mv EXCEPT ALL SELECT * FROM v) UNION ALL
|
|
(SELECT * FROM v EXCEPT ALL SELECT * FROM mv)) $$ LANGUAGE sql;
|
|
}
|
|
|
|
teardown
|
|
{
|
|
DROP FUNCTION check_mv();
|
|
DROP TABLE mv;
|
|
DROP VIEW v;
|
|
DROP TABLE a;
|
|
}
|
|
|
|
session tx1
|
|
setup { BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; }
|
|
step s1 { SELECT; }
|
|
step refresh { SELECT pgivm.refresh_immv('mv', true); }
|
|
step check1 {SELECT check_mv();}
|
|
step c1 { COMMIT; }
|
|
step mv { SELECT * FROM mv ORDER BY 1,2; SELECT check_mv(); }
|
|
|
|
session tx2
|
|
setup { BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; }
|
|
step s2 { SELECT; }
|
|
step insert { INSERT INTO a VALUES (2); }
|
|
step check2 {SELECT check_mv(); }
|
|
step c2 { COMMIT; }
|
|
|
|
permutation s1 refresh s2 insert c1 check2 c2 mv
|
|
permutation s1 refresh s2 c1 insert check2 c2 mv
|
|
permutation s1 s2 refresh insert c1 check2 c2 mv
|
|
permutation s1 s2 insert refresh c2 check1 c1 mv
|
|
permutation s1 s2 refresh c1 insert check2 c2 mv
|
|
permutation s2 insert s1 refresh c2 check1 c1 mv
|
|
permutation s2 insert s1 c2 refresh check1 c1 mv
|
|
permutation s2 s1 insert c2 refresh check1 c1 mv
|