函数支持自治事务

自治事务可以在函数中定义，标识符为PRAGMA AUTONOMOUS_TRANSACTION，其余语法与函数语法相同，请参见CREATE FUNCTION，示例如下。

gaussdb=# CREATE TABLE t4(a INT, b INT, c TEXT);
NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using 'a' as the distribution column by default.
HINT:  Please use 'DISTRIBUTE BY' clause to specify suitable data distribution column.
CREATE TABLE

gaussdb=# CREATE OR REPLACE FUNCTION autonomous_32(a INT ,b INT ,c TEXT) RETURN INT AS 
DECLARE 
	PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
	INSERT INTO t4 VALUES(a, b, c);
	RETURN 1;
END;
/
CREATE FUNCTION
gaussdb=# CREATE OR REPLACE FUNCTION autonomous_33(num1 INT) RETURN INT AS 
DECLARE 
	num3 INT := 220;
	tmp INT;
	PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
	num3 := num3/num1;
	RETURN num3;
EXCEPTION
	WHEN DIVISION_BY_ZERO THEN
		SELECT autonomous_32(num3, num1, SQLERRM) INTO tmp;
		ROLLBACK;
		RETURN 0;
END;
/
CREATE FUNCTION
gaussdb=# SELECT autonomous_33(0);
 autonomous_33 
---------------
             0
(1 row)

gaussdb=# SELECT * FROM t4;
  a  | b |        c         
-----+---+------------------
 220 | 0 | division by zero
(1 row)

gaussdb=# DROP TABLE t4;
DROP TABLE

上述例子，最后在回滚的事务块中执行包含自治事务的函数，也能直接说明了自治事务的特性，即主事务的回滚，不会影响自治事务已经提交的内容。