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

Vadim wrote:
>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;
2 rows updated.
>5.  in session T1 run
>    SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>    UPDATE test SET y = 3 WHERE x = 1;
blocks
>    --
>    -- 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 -:)
UPDATE test SET y = 3 WHERE x = 1
       *
ERROR at line 1:
ORA-08177: can't serialize access for this transaction
SQL> rollback;

Rollback complete.
>8.  now in session T2 run
>    UPDATE test SET x = 2;
3 rows updated.
>9.  in session T1 run
>    SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
>    UPDATE test SET y = 4 WHERE x = 1 or x = 2;
blocks
>11. in session T2 run
>    COMMIT;
Commit complete.
in T1: 3 rows updated.
>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

So it does.

Andreas