Oracle Autonomous Transactions（自治事务）(二)
ONOMOUS_TRANSACTION;
BEGIN
INSERT INTO error_logs (id, log_timestamp, error_message)
VALUES (error_logs_seq.NEXTVAL, SYSTIMESTAMP, p_error_message);
COMMIT;
END;
/
The following code forces an error, which is trapped and logged.
BEGIN
INSERT INTO at_test (id, description)
VALUES (998, 'Description for 998');
-- Force invalid insert.
INSERT INTO at_test (id, description)
VALUES (999, NULL);
EXCEPTION
WHEN OTHERS THEN
log_errors (p_error_message => SQLERRM);
ROLLBACK;
END;
/
PL/SQL procedure successfully completed.
SELECT * FROM at_test WHERE id >= 998;
no rows selected
SELECT * FROM error_logs;
ID LOG_TIMESTAMP
---------- ---------------------------------------------------------------------------
ERROR_MESSAGE
----------------------------------------------------------------------------------------------------
1 28-FEB-2006 11:10:10.107625
ORA-01400: cannot insert NULL into ("TIM_HALL"."AT_TEST"."DESCRIPTION")
1 row selected.
SQL>
From this we can see that the LOG_ERRORS transaction was separate to the anonymous block. If it weren't, we would expect the first insert in the anonymous block to be preserved by the commit statement in the LOG_ERRORSprocedure.
Be careful how you use autonomous transactions. If they are used indiscriminately they can lead to deadlocks, and cause confusion when analyzing session trace. To hammer this point home, here's a quote from Tom Kyte.
"... in 999 times out of 1000, if you find yourself "forced" to use an autonomous transaction - it likely means you have a serious data integrity issue you haven't thought about.
Where do people try to use them
in that trigger that calls a procedure that commits (not an error logging routine). Ouch, that has to hurt when you rollback.
in that trigger that is getting the mutating table constraint. Ouch, that hurts *even more*
Error logging - OK.
Almost everything else - not OK."