Doc Map

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/SAVEPOINT can be used in stored procedures in PL/SQL.
  • 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 contexts and statements in PLSQL.
  • 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 PLSQL, such as PLJava and PLPython.
  • 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.
  • 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 stored procedures in PLSQL.

    CREATE TABLE EXAMPLE1(COL1 INT);

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;
/

  • 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 or ROLLBACK can be committed or rolled back.

    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;
/

  • 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.

    BEGIN;
    CALL TEST_COMMIT_INSERT_EXCEPTION_ROLLBACK();
END;

  • Example 4: COMMIT/ROLLBACK, including IF, FOR, CURSOR LOOP, and WHILE, can be called in most PLSQL contexts and statements.

    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;
/

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

    CREATE OR REPLACE PROCEDURE exec_func3(RET_NUM OUT INT)
AS
BEGIN
    RET_NUM := 1+1;
COMMIT;
END;
/
CREATE OR REPLACE PROCEDURE exec_func4(ADD_NUM IN INT)
AS
SUM_NUM INT;
BEGIN
SUM_NUM := ADD_NUM + exec_func3();
COMMIT;
END;
/

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

    SHOW explain_perf_mode;
SHOW enable_force_vector_engine;

CREATE OR REPLACE PROCEDURE GUC_ROLLBACK()
AS
BEGIN
    SET enable_force_vector_engine = on;
    COMMIT;
    SET explain_perf_mode TO pretty;
    ROLLBACK;
END;
/

call GUC_ROLLBACK();
SHOW explain_perf_mode;
SHOW enable_force_vector_engine;
SET enable_force_vector_engine = off;

  • Example 7: COMMIT, ROLLBACK, and stored procedures that contain COMMIT or ROLLBACK cannot be called in functions.

    CREATE OR REPLACE FUNCTION FUNCTION_EXAMPLE1() RETURN INT
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;
    RETURN EXP;
END;
/

  • Example 8: Stored procedures that contain COMMIT or ROLLBACK cannot be called in functions.

    CREATE OR REPLACE FUNCTION FUNCTION_EXAMPLE2() RETURN INT
AS
EXP INT;
BEGIN
    -- transaction_example is a stored procedure and contains the COMMIT/ROLLBACK statement.
    CALL transaction_example();
    SELECT COUNT(*) FROM EXAMPLE1 INTO EXP;
    RETURN EXP;
END;
/

  • Example 9: A TRIGGER stored procedure cannot contain COMMIT or ROLLBACK or call another stored procedure that contains COMMIT or ROLLBACK.

    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 TRIGGER TRIGGER_EXAMPLE AFTER DELETE ON EXAMPLE1 
FOR EACH ROW EXECUTE PROCEDURE FUNCTION_TRI_EXAMPLE2();

DELETE FROM EXAMPLE1;

  • Example 10: Stored procedures that contain IMMUTABLE or SHIPPABLE cannot call COMMIT, ROLLBACK, or another stored procedure that contains COMMIT or ROLLBACK.

    CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE1()
IMMUTABLE
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;
/

  • Example 12: Calling in SQL statements (other than Select Procedure) is not supported.

    CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE3()
AS
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;
END;
/

  • Example 13: COMMIT or ROLLBACK cannot be called in a stored procedure whose header contains GUC parameters.

    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;
/

  • Example 14: A stored procedure whose cursor is open cannot contain COMMIT or ROLLBACK.

    CREATE OR REPLACE PROCEDURE TRANSACTION_EXAMPLE5(INTIN IN INT, INTOUT OUT INT)
AS
BEGIN
INTOUT := INTIN + 1;
COMMIT;
END;
/

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; 
/

  • Example 15: COMMIT or ROLLBACK cannot be called in expressions or CURSOR and EXECUTE statements.

    CREATE OR REPLACE PROCEDURE exec_func1()
AS
BEGIN
    CREATE TABLE TEST_exec(A INT);
COMMIT;
END;
/
CREATE OR REPLACE PROCEDURE exec_func2()
AS
BEGIN
EXECUTE exec_func1();
COMMIT;
END;
/

  • Example 16: Roll back some modifications of stored procedure on a transaction to a savepoint.

    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;
/

  • Example 17: Roll back a stored procedure to a savepoint defined outside the stored procedure.

    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;
/

BEGIN;
INSERT INTO EXAMPLE1 VALUES(1);
SAVEPOINT s1;
CALL STP_SAVEPOINT_EXAMPLE2();
SELECT * FROM EXAMPLE1;
COMMIT;

  • Example 18: Roll back an external SQL or other stored procedure to a savepoint defined in the stored procedure.

    CREATE OR REPLACE PROCEDURE STP_SAVEPOINT_EXAMPLE3()
AS
BEGIN
    INSERT INTO EXAMPLE1 VALUES(1);
    SAVEPOINT s1;
    INSERT INTO EXAMPLE1 VALUES(2);
END;
/

BEGIN;
INSERT INTO EXAMPLE1 VALUES(3);
CALL STP_SAVEPOINT_EXAMPLE3();
ROLLBACK TO SAVEPOINT s1; -- Roll back the insertion of record 2 to the stored procedure.
SELECT * FROM EXAMPLE1;
COMMIT;
Feedback
编组 3备份

您对 openGauss文档 的整体满意度如何？

0
0-不满意10-非常满意

0/500

感谢您的反馈，如需帮助可联系contact@opengauss.org

问题反馈

contact@opengauss.org

    openGauss 2024-11-22 00:52:56
    cancel