Transaction Management

Calling a stored procedure automatically starts a transaction. When the calling is complete, the transaction is automatically committed, or rolled back upon an exception. In addition to automatic transaction control, you can also use COMMIT/ROLLBACK to control transactions in stored procedures. Running the COMMIT/ROLLBACK commands in a stored procedure will commit or roll back the current transaction and automatically starts a new transaction. All subsequent operations will be performed in the new transaction.

A savepoint is a special mark inside a transaction. It allows all commands that are executed after it was established to be rolled back, restoring the transaction state to what it was at the time of the savepoint. In a stored procedure, you can use savepoints to manage transactions. Currently, you can create, roll back, and release savepoints. If a savepoint for rollback is used in a stored procedure, only the modification of the current transaction is rolled back. The execution process of the stored procedure is not changed, and the values of local variables in the stored procedure are not rolled back.

Syntax

Define a savepoint.
    SAVEPOINT savepoint_name;
Roll back a savepoint.
    ROLLBACK TO [SAVEPOINT] savepoint_name;
Release a savepoint.
    RELEASE [SAVEPOINT] savepoint_name;

Usage Scenarios

The applicable contexts are as follows:

COMMIT, ROLLBACK, and SAVEPOINT can be used in PL/SQL stored procedures.
COMMIT, ROLLBACK, and SAVEPOINT can be used in stored procedures that contain EXCEPTION.
COMMIT, ROLLBACK, and SAVEPOINT can be used in EXCEPTION statements of stored procedures.
A stored procedure that contains COMMIT, ROLLBACK, or SAVEPOINT (which means the stored procedure is controlled by BEGIN, START, or END) can be called in a transaction block.
A stored procedure that contains savepoints can be invoked in a subtransaction. That is, an externally defined savepoint is used in the stored procedure to roll back the transaction to the savepoint defined outside the stored procedure.
A stored procedure is visible to a savepoint defined in the stored procedure. That is, the modification of the transaction can be rolled back to the savepoint defined in the stored procedure.
COMMIT, ROLLBACK, and SAVEPOINT, as well as IF, FOR, CURSOR LOOP, and WHILE, can be called in most PL/SQL contexts and statements.
A stored procedure or function that contains COMMIT, ROLLBACK, or SAVEPOINT can be called in the return values and simple expression calculation of stored procedures.

The following content can be committed or rolled back:

DDL statements after COMMIT/ROLLBACK can be committed or rolled back.
DML statements after COMMIT/ROLLBACK can be committed.
GUC parameters in stored procedures can be committed or rolled back.

Usage Restrictions

COMMIT and ROLLBACK cannot be used in the following contexts:

COMMIT, ROLLBACK, and SAVEPOINT cannot be called in stored procedures other than PL/SQL, such as PL/Java and PL/Python.
COMMIT, ROLLBACK, SAVEPOINT and stored procedures that contain COMMIT, ROLLBACK, or SAVEPOINT cannot be called in functions.
After SAVEPOINT is called in a transaction block, stored procedures that contain COMMIT/ROLLBACK cannot be called.
Stored procedures that contain COMMIT, ROLLBACK, or SAVEPOINT cannot be called in TRIGGER.
COMMIT, ROLLBACK, and SAVEPOINT cannot be invoked in EXECUTE statements.
Stored procedures that contain COMMIT, ROLLBACK, or SAVEPOINT cannot be called in CURSOR statements.
Stored procedures that contain IMMUTABLE or SHIPPABLE cannot call COMMIT, ROLLBACK, SAVEPOINT or another stored procedure that contain COMMIT, ROLLBACK, or SAVEPOINT.
Stored procedures that contain COMMIT, ROLLBACK, or SAVEPOINT cannot be called in SQL statements other than SELECT PROC and CALL PROC.
COMMIT, ROLLBACK, or SAVEPOINT cannot be called in a stored procedure whose header contains GUC parameters.
COMMIT, ROLLBACK, or SAVEPOINT cannot be called in expressions or CURSOR and EXECUTE statements.
Savepoints defined outside a stored procedure cannot be released in the stored procedure.
An autonomous transaction and a stored procedure transaction are two independent transactions that cannot use the savepoints defined in each other.

The following content cannot be committed or rolled back:

Variables declared or imported in stored procedures cannot be committed or rolled back.
In stored procedures, GUC parameters that take effect only after a restart cannot be committed or rolled back.

Examples

Example 1: COMMIT/ROLLBACK can be used in PL/SQL stored procedures. Subsequent examples depend on this case.

gaussdb=# DROP TABLE IF EXISTS EXAMPLE1; 
NOTICE:  table "example1" does not exist, skipping
DROP TABLE
gaussdb=# CREATE TABLE EXAMPLE1(COL1 INT);
CREATE TABLE
gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE()
AS
BEGIN
    FOR i IN 0..20 LOOP
        INSERT INTO EXAMPLE1(COL1) VALUES (i);
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
    END LOOP;
END;
/
CREATE PROCEDURE
gaussdb=# CALL TRANSACTION_EXAMPLE();
 transaction_example 
---------------------

(1 row)

Example 2:

COMMIT and ROLLBACK can be used in stored procedures that contain EXCEPTION.

COMMIT and ROLLBACK can be used in EXCEPTION statements of stored procedures.

DDL statements after COMMIT/ROLLBACK can be committed or rolled back.

gaussdb=# CREATE OR REPLACE PROCEDURE TEST_COMMIT_INSERT_EXCEPTION_ROLLBACK()
AS
BEGIN
 DROP TABLE IF EXISTS TEST_COMMIT; 
 CREATE TABLE TEST_COMMIT(A INT, B INT);
 INSERT INTO TEST_COMMIT SELECT 1, 1;
 COMMIT;
        CREATE TABLE TEST_ROLLBACK(A INT, B INT);
 RAISE EXCEPTION 'RAISE EXCEPTION AFTER COMMIT';
EXCEPTION
    WHEN OTHERS THEN
 INSERT INTO TEST_COMMIT SELECT 2, 2;
 ROLLBACK;
END;
/
CREATE PROCEDURE
gaussdb=# CALL TEST_COMMIT_INSERT_EXCEPTION_ROLLBACK();
NOTICE:  table "test_commit" does not exist, skipping
CONTEXT:  SQL statement "DROP TABLE IF EXISTS TEST_COMMIT"
PL/pgSQL function test_commit_insert_exception_rollback() line 3 at SQL statement
 test_commit_insert_exception_rollback 
---------------------------------------

(1 row)

Example 3: A stored procedure that contains COMMIT or ROLLBACK (which means the stored procedure is controlled by BEGIN, START, or END) can be called in a transaction block.

gaussdb=# BEGIN;
    -- For the definition of TEST_COMMIT_INSERT_EXCEPTION_ROLLBACK, see example 2.
    CALL TEST_COMMIT_INSERT_EXCEPTION_ROLLBACK();
END;
 test_commit_insert_exception_rollback 
---------------------------------------

(1 row)
COMMIT

Example 4: COMMIT and ROLLBACK, as well as IF, FOR, CURSOR LOOP, and WHILE, can be called in most PL/SQL contexts and statements.

gaussdb=# CREATE OR REPLACE PROCEDURE TEST_COMMIT2()
IS
BEGIN
    DROP TABLE IF EXISTS TEST_COMMIT;
    CREATE TABLE TEST_COMMIT(A INT);
    FOR I IN REVERSE 3..0 LOOP
 INSERT INTO TEST_COMMIT SELECT I;
 COMMIT;
    END LOOP;
    FOR I IN REVERSE 2..4 LOOP
 UPDATE TEST_COMMIT SET A=I;
 COMMIT;
    END LOOP;
EXCEPTION
WHEN OTHERS THEN   
 INSERT INTO TEST_COMMIT SELECT 4;
    COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CALL TEST_COMMIT2();
 test_commit2 
--------------

(1 row)

Example 5: Return values and simple expression calculation of stored procedures are supported.

gaussdb=# CREATE OR REPLACE PROCEDURE exec_func3(RET_NUM OUT INT)
AS
BEGIN
    RET_NUM := 1+1;
COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CALL exec_func3('');
 ret_num 
---------
       2
(1 row)
gaussdb=# CREATE OR REPLACE PROCEDURE exec_func4(ADD_NUM IN INT)
AS
SUM_NUM INT;
BEGIN
SUM_NUM := ADD_NUM + exec_func3();
COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CALL exec_func4(1);
 exec_func4 
------------

(1 row)

Example 6: GUC parameters in stored procedures can be rolled back to a commit.

gaussdb=# SET explain_perf_mode='normal';
SET
gaussdb=# SHOW explain_perf_mode;
 explain_perf_mode 
-------------------
 normal
(1 row)
gaussdb=# SHOW enable_force_vector_engine;
 enable_force_vector_engine 
----------------------------
 off
(1 row)
gaussdb=# CREATE OR REPLACE PROCEDURE GUC_ROLLBACK()
AS
BEGIN
    SET enable_force_vector_engine = on;
    COMMIT;
    SET explain_perf_mode TO pretty;
    ROLLBACK;
END;
/
CREATE PROCEDURE
gaussdb=# CALL GUC_ROLLBACK();
 guc_rollback 
--------------

(1 row)
gaussdb=# SHOW explain_perf_mode;
 explain_perf_mode 
-------------------
 normal
(1 row)
gaussdb=# SHOW enable_force_vector_engine;
 enable_force_vector_engine 
----------------------------
 on
(1 row)
gaussdb=# SET enable_force_vector_engine = off;
SET

Example 7: A TRIGGER stored procedure cannot contain COMMIT or ROLLBACK or call another stored procedure that contains COMMIT or ROLLBACK.

gaussdb=# CREATE OR REPLACE FUNCTION FUNCTION_TRI_EXAMPLE2() RETURN TRIGGER
AS
EXP INT;
BEGIN
    FOR i IN 0..20 LOOP
        INSERT INTO EXAMPLE1(col1) VALUES (i);
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
    END LOOP;
    SELECT COUNT(*) FROM EXAMPLE1 INTO EXP;
END;
/
CREATE FUNCTION
gaussdb=# CREATE TRIGGER TRIGGER_EXAMPLE AFTER DELETE ON EXAMPLE1 
FOR EACH ROW EXECUTE PROCEDURE FUNCTION_TRI_EXAMPLE2();
CREATE TRIGGER
gaussdb=# DELETE FROM EXAMPLE1;
ERROR:  Can not commit/rollback if it's atomic is true: can not use commit rollback in Complex SQL
CONTEXT:  PL/pgSQL function function_tri_example2() line 7 at COMMIT

Example 8: Stored procedures that contain IMMUTABLE or SHIPPABLE cannot call COMMIT, ROLLBACK, or another stored procedure that contains COMMIT or ROLLBACK.

gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE1()
IMMUTABLE
AS
EXP INT;
BEGIN
    FOR i IN 0..20 LOOP
        SELECT COUNT(*) FROM EXAMPLE1 INTO EXP;
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
    END LOOP;
END;
/
CREATE PROCEDURE
gaussdb=#CALL TRANSACTION_EXAMPLE1();
ERROR:  Can not commit/rollback if it's atomic is true: commit/rollback/savepoint is not allowed in a non-volatile function
CONTEXT:  PL/pgSQL function transaction_example1() line 7 at COMMIT

Example 9: Variables declared or passed in stored procedures cannot be committed.

gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE2(EXP_OUT OUT INT)
AS
EXP INT:=-1;
BEGIN
    EXP_OUT := 0;
    EXP := 0;
    COMMIT;
    DBE_OUTPUT.PRINT_LINE('EXP IS:'||EXP);
    DBE_OUTPUT.PRINT_LINE('EXP_OUT IS:'||EXP_OUT);
    EXP := 1;
    EXP_OUT := 1;
    ROLLBACK;
    DBE_OUTPUT.PRINT_LINE('EXP IS:'||EXP);
    DBE_OUTPUT.PRINT_LINE('EXP_OUT IS:'||EXP_OUT);
END;
/
CREATE PROCEDURE
gaussdb=# CALL TRANSACTION_EXAMPLE2(1);
EXP IS:0
EXP_OUT IS:0
EXP IS:1
EXP_OUT IS:1
 exp_out 
---------
       1
(1 row)

Example 10: Calling in SQL statements (other than Select Procedure) is not supported.

gaussdb=# CREATE OR REPLACE FUNCTION TRANSACTION_EXAMPLE3()
RETURN INT
IS
BEGIN
    FOR i IN 0..20 LOOP
        INSERT INTO EXAMPLE1 (col1) VALUES (i);
        IF i % 2 = 0 THEN
            EXECUTE IMMEDIATE 'COMMIT';
        ELSE
            EXECUTE IMMEDIATE 'ROLLBACK';
        END IF;
    END LOOP;
    RETURN 1;
END;
/
CREATE PROCEDURE
gaussdb=# SELECT * FROM example1 WHERE col1=TRANSACTION_EXAMPLE3();
ERROR:  cannot call transaction statements in EXECUTE IMMEDIATE statement.
CONTEXT:  PL/pgSQL function transaction_example3() line 6 at EXECUTE statement

Example 11: COMMIT or ROLLBACK cannot be called in a stored procedure whose header contains GUC parameters.

gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE4()
SET ARRAY_NULLS TO "ON"
AS
BEGIN
    FOR i IN 0..20 LOOP
        INSERT INTO EXAMPLE1 (col1) VALUES (i);
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
    END LOOP;
END;
/
CREATE PROCEDURE
gaussdb=# CALL TRANSACTION_EXAMPLE4();
ERROR:  Can not commit/rollback if it's atomic is true: transaction statement in store procedure with GUC setting in option clause is not supported
CONTEXT:  PL/pgSQL function transaction_example4() line 6 at COMMIT

Example 12: A stored procedure whose cursor is open cannot contain COMMIT or ROLLBACK.

gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE5(INTIN IN INT, INTOUT OUT INT)
AS
BEGIN
INTOUT := INTIN + 1;
COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE6()
AS
CURSOR CURSOR1(EXPIN INT)
IS SELECT TRANSACTION_EXAMPLE5(EXPIN);
INTEXP INT;
BEGIN
    FOR i IN 0..20 LOOP
        OPEN CURSOR1(i);
        FETCH CURSOR1 INTO INTEXP;
        INSERT INTO EXAMPLE1(COL1) VALUES (INTEXP);
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
        CLOSE CURSOR1;
    END LOOP;
END; 
/
CREATE PROCEDURE
gaussdb=# CALL TRANSACTION_EXAMPLE6();
ERROR:  Can not commit/rollback if it's atomic is true: transaction statement in store procedure used as cursor is not supported
CONTEXT:  PL/pgSQL function transaction_example5(integer) line 4 at COMMIT
referenced column: transaction_example5
PL/pgSQL function transaction_example6() line 8 at FETCH

Example 13: COMMIT or ROLLBACK cannot be called in expressions or CURSOR and EXECUTE statements.

gaussdb=# CREATE OR REPLACE PROCEDURE exec_func1()
AS
BEGIN
    CREATE TABLE TEST_exec(A INT);
COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CREATE OR REPLACE PROCEDURE exec_func2()
AS
BEGIN
EXECUTE exec_func1();
COMMIT;
END;
/
CREATE PROCEDURE
gaussdb=# CALL exec_func2();
ERROR:  Can not commit/rollback if it's atomic is true: transaction statement in store procedure used as a expression is not supported
CONTEXT:  PL/pgSQL function exec_func1() line 4 at COMMIT
PL/pgSQL function exec_func2() line 3 at EXECUTE statement

Example 14: Roll back some modifications of stored procedure on a transaction to a savepoint.

gaussdb=# CREATE OR REPLACE PROCEDURE STP_SAVEPOINT_EXAMPLE1()
AS
BEGIN
    INSERT INTO EXAMPLE1 VALUES(1);
    SAVEPOINT s1;
    INSERT INTO EXAMPLE1 VALUES(2);
    ROLLBACK TO s1;  -- Roll back the insertion of record 2.
    INSERT INTO EXAMPLE1 VALUES(3);
END;
/
CREATE PROCEDURE
gaussdb=# CALL STP_SAVEPOINT_EXAMPLE1();
 stp_savepoint_example1 
------------------------

(1 row)

Example 15: Roll back a stored procedure to a savepoint defined outside the stored procedure.

gaussdb=# TRUNCATE TABLE EXAMPLE1;
TRUNCATE TABLE
gaussdb=# CREATE OR REPLACE PROCEDURE STP_SAVEPOINT_EXAMPLE2()
AS
BEGIN
    INSERT INTO EXAMPLE1 VALUES(2);
    ROLLBACK TO s1;  -- Roll back the insertion of record 2.
    INSERT INTO EXAMPLE1 VALUES(3);
END;
/
CREATE PROCEDURE
gaussdb=# BEGIN;
BEGIN
gaussdb=# INSERT INTO EXAMPLE1 VALUES(1);
INSERT 0 1
gaussdb=# SAVEPOINT s1;
SAVEPOINT
gaussdb=# CALL STP_SAVEPOINT_EXAMPLE2();
 stp_savepoint_example2 
------------------------

(1 row)
gaussdb=# SELECT * FROM EXAMPLE1;
 col1 
------
    1
    3
(2 rows)
gaussdb=# COMMIT;
COMMIT

Example 16: Savepoints defined outside the stored procedure cannot be released in the stored procedure.

gaussdb=# CREATE OR REPLACE PROCEDURE STP_SAVEPOINT_EXAMPLE3()
AS
BEGIN
    INSERT INTO EXAMPLE1 VALUES(2);
    RELEASE SAVEPOINT s1; -- Release the savepoint defined outside the stored procedure.
    INSERT INTO EXAMPLE1 VALUES(3);
END;
/
CREATE PROCEDURE
gaussdb=# BEGIN;
BEGIN
gaussdb=# INSERT INTO EXAMPLE1 VALUES(1);
INSERT 0 1
gaussdb=# SAVEPOINT s1;
SAVEPOINT
gaussdb=# CALL STP_SAVEPOINT_EXAMPLE3();
ERROR:  cannot release outer savepoint
CONTEXT:  PL/pgSQL function stp_savepoint_example3() line 4 at RELEASE SAVEPOINT
gaussdb=# COMMIT;
ROLLBACK

Example 17: Roll back an external SQL or other stored procedure to a savepoint defined in the stored procedure.

gaussdb=# TRUNCATE TABLE EXAMPLE1;
TRUNCATE TABLE
gaussdb=# CREATE OR REPLACE PROCEDURE STP_SAVEPOINT_EXAMPLE4()
AS
BEGIN
    INSERT INTO EXAMPLE1 VALUES(1);
    SAVEPOINT s1;
    INSERT INTO EXAMPLE1 VALUES(2);
END;
/
CREATE PROCEDURE
gaussdb=# BEGIN;
BEGIN
gaussdb=# INSERT INTO EXAMPLE1 VALUES(3);
INSERT 0 1
gaussdb=# CALL STP_SAVEPOINT_EXAMPLE4();
 stp_savepoint_example4 
------------------------

(1 row)
gaussdb=# ROLLBACK TO SAVEPOINT s1; -- Roll back the insertion of record 2 to the stored procedure.
ROLLBACK
gaussdb=# SELECT * FROM EXAMPLE1;
 col1 
------
    3
    1
(2 rows)
gaussdb=# COMMIT;
COMMIT