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:: How Commit Works in PL SQL Functions/Triggers ::

COMMIT in Functions/Triggers.
+++++++++++++++++++

It Triggers/functions may be led to bulk associated transactions. This may lead to transaction atomicity failure.

Please find the below test case from Oracle.

Step 1:
---------

SQL> CREATE TABLE COMMIT_TRIG_TEST_TABLE1(T INT);

Table created.

SQL> CREATE TABLE COMMIT_TRIG_TEST_TABLE2(T INT,CHECK (T NOT IN(0)));

Table created.

Step 2:
---------
CREATE OR REPLACE FUNCTION INSERT_DATA(NUM IN NUMBER)
RETURN VARCHAR2 IS
BEGIN
EXECUTE IMMEDIATE 'INSERT INTO COMMIT_TRIG_TEST_TABLE1 VALUES('||NUM||')';
RETURN 'INSERT OK';
END;

Step 3:
---------
CREATE OR REPLACE TRIGGER COMMIT_TRIG
BEFORE INSERT ON COMMIT_TRIG_TEST_TABLE1
FOR EACH ROW
DECLARE
BEGIN
INSERT INTO COMMIT_TRIG_TEST_TABLE2 VALUES(:NEW.T);
END;

Step 4:
--------
However, we know that if the function having dml operations, then we can't make that function as a part of SQL statement. So, please use the below method for inserting

the data.

SQL> VAR V VARCHAR2(10);
SQL> EXEC :V :=INSERT_DATA(10);

PL/SQL procedure successfully completed.

SQL> PRINT V;

V
------------------
INSERT OK

Please observer this statement in INSERT_DATA function .

This insert statement is associated with two transactions.

1. By itself.

2.INSERT INTO COMMIT_TRIG_TEST_TABLE2 VALUES:

InTrigger Body Asper Atomocity(ACID), whether the transaction must Commit/Rollback.


+INSERT ON TABLE1 (Success)+ }

==> TRANSACTION is sucess.

+INSERT ON TABLE2 (Success)+ }


SQL> SELECT * FROM COMMIT_TRIG_TEST_TABLE1;

T
----------
10

SQL> SELECT * FROM COMMIT_TRIG_TEST_TABLE2;

T
----------
10


That's why this EXEC :V :=INSERT_DATA(10) is sucessfull.

Step 5
--------

SQL> DELETE FROM COMMIT_TRIG_TEST_TABLE1;

SQL> DELETE FROM COMMIT_TRIG_TEST_TABLE2;

SQL> exec :v :=insert_data(0);
BEGIN :v :=insert_data(0); END;
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.SYS_C009672) violated
ORA-06512: at "SCOTT.COMMIT_TRIG", line 3
ORA-04088: error during execution of trigger 'SCOTT.COMMIT_TRIG'
ORA-06512: at "SCOTT.INSERT_DATA", line 4
ORA-06512: at line 1

Here the transactions are as below

+INSERT ON TABLE1 (Success)+}

==> TRANSACTION is failure.

+INSERT ON TABLE2 (Failure)+}

As per Automocity rule, whether the transaction must be sucess/fail. However, here the transaction is having both.

That's why the total transaction is rolled back. So, INSERT ON TABLE1 also rolled back here.

SQL> SELECT * FROM COMMIT_TRIG_TEST_TABLE1;

no rows selected

SQL> SELECT * FROM COMMIT_TRIG_TEST_TABLE2;

no rows selected

Even though if you have autonomous_transactions, those must and should statisfy this automoctiy.


Now, how to insert element '0' in first table.

Step 6
--------

CREATE OR REPLACE FUNCTION INSERT_DATA(NUM IN NUMBER)
RETURN VARCHAR2 IS
pragma autonomous_transaction;
BEGIN
INSERT INTO COMMIT_TRIG_TEST_TABLE1 VALUES(NUM);
COMMIT;
RETURN 'INSERT OK';
END;

Need to make the trigger always commits.Even though it fails, it needs to commit for satisfying the automocity.

CREATE OR REPLACE TRIGGER COMMIT_TRIG
BEFORE INSERT ON COMMIT_TRIG_TEST_TABLE1
FOR EACH ROW
DECLARE
pragma autonomous_transaction;
BEGIN
INSERT INTO COMMIT_TRIG_TEST_TABLE2 VALUES(:NEW.T);
commit;
exception when others then
COMMIT;
END;

SQL> select insert_data(0) from dual;

INSERT_DATA(0)
--------------------------------------------------------------------------------
INSERT OK


SQL> select * from commit_trig_test_table1;

T
----------
0

SQL> select * from commit_trig_test_table2;

no rows selected


--Dinesh

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