Re: [HACKERS] Q about read committed in Oracle...

From: Vadim Mikheev <vadim(at)krs(dot)ru>
To: "Dr(dot) Michael Meskes" <meskes(at)online-club(dot)de>
Cc: hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Q about read committed in Oracle...
Date: 1998-07-30 08:40:13
Message-ID: 35C0316D.79A31891@krs.ru
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First, thanks Michael!

It's nice to see expected results but I still have some
new questions - please help!

1. CREATE TABLE test (x integer, y integer)
2. INSERT INTO test VALUES (1, 1);
INSERT INTO test VALUES (1, 2);
INSERT INTO test VALUES (3, 2);
3. run two session T1 and T2
4. in session T2 run
UPDATE test SET x = 1, y = 2 WHERE x <> 1 OR y <> 2;
5. in session T1 run
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
UPDATE test SET y = 3 WHERE x = 1;
--
-- 1st record will be changed by T2, qual for new record
-- version will be OK, but T1 should be aborted (???)
--
6. in session T2 run
COMMIT;
7. in session T1 run
ROLLBACK; -- just to be sure -:)
8. now in session T2 run
UPDATE test SET x = 2;
9. in session T1 run
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
UPDATE test SET y = 4 WHERE x = 1 or x = 2;
11. in session T2 run
COMMIT;
12. in session T1 run
SELECT * FROM test; -- results?
^^^^^^^^^^^^^^^^^^
I would like to be sure that T1 will update table...

TIA,
Vadim

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