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

On Thu, Jul 30, 1998 at 04:40:13PM +0800, Vadim Mikheev wrote:
> 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;

UPDATE test SET y = 3 WHERE x = 1
*
ERROR at line 1:
ORA-08177: can't serialize access for this transaction

> --
> -- 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;

blocked

> 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...

X Y
---------- ----------
2 4
2 4
2 4

Michael
--
Dr. Michael Meskes meskes(at)online-club(dot)de, meskes(at)debian(dot)org
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