Restrictions

When an autonomous transaction is executed, an autonomous transaction session is started in the background. You can use max_concurrent_autonomous_transactions to set the maximum number of concurrent autonomous transactions. The value range is 0 to 10000, and the default value is 10.
When max_concurrent_autonomous_transactions is set to 0, autonomous transactions cannot be executed.
After a new session is started for an autonomous transaction, the default session parameters are used and objects (including session-level variables, local temporary variables, and global temporary table data) of the primary session are not shared.
Theoretically, the upper limit of autonomous transactions is 10000. Actually, the upper limit is a dynamic value. For details, see the description of the GUC parameter max_concurrent_autonomous_transactions.
Autonomous transactions are affected by the communication buffer. The size of the information returned to the client is limited by the length of the communication buffer. If the size exceeds the length of the communication buffer, an error is reported.

A trigger function does not support autonomous transactions.

gaussdb=# CREATE TABLE test_trigger_des_tbl(id1 int, id2 int, id3 int);
CREATE TABLE

gaussdb=# CREATE OR REPLACE FUNCTION tri_insert_func() RETURNS TRIGGER AS
$$
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
INSERT INTO test_trigger_des_tbl VALUES(new.id1, new.id2, new.id3);
RETURN new;
END$$ LANGUAGE plpgsql;
ERROR:  Triggers do not support autonomous transactions
DETAIL:  N/A

gaussdb=# DROP TABLE test_trigger_des_tbl;
DROP TABLE

Autonomous transactions cannot be called by non-top-layer anonymous blocks (but can only be called by top-layer autonomous transactions, including stored procedures, functions, and anonymous blocks).

gaussdb=# CREATE TABLE t1(a INT ,b TEXT);
CREATE TABLE

gaussdb=# DECLARE 
--PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
DECLARE 
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
DBE_OUTPUT.PRINT_LINE('JUST USE CALL.');
INSERT INTO t1 VALUES(1,'CAN YOU ROLLBACK!');
END;
INSERT INTO t1 VALUES(2,'I WILL ROLLBACK!');
ROLLBACK;
END;
/
JUST USE CALL.
ANONYMOUS BLOCK EXECUTE
gaussdb=# SELECT * FROM t1;
 a | b 
---+---
(0 rows)

gaussdb=# DROP TABLE t1;
DROP TABLE

In an autonomous transaction, the ref cursor parameter can be passed only through the PROCEDURE OUT parameter. The ref cursor parameter cannot be passed through IN, INOUT, or FUNCTION. In a stored procedure, the ref cursor parameter can be passed only through the OUT parameter of an autonomous transaction. The ref cursor parameter cannot be directly called on the client (such as gsql and JDBC).

-- Create a table.
gaussdb=# CREATE TABLE sections(section_id INT);
CREATE TABLE
gaussdb=# INSERT INTO sections VALUES(1);
INSERT 0 1
gaussdb=# INSERT INTO sections VALUES(1);
INSERT 0 1
gaussdb=# INSERT INTO sections VALUES(1);
INSERT 0 1
gaussdb=# INSERT INTO sections VALUES(1);
INSERT 0 1

The PROCEDURE OUT output parameter passes the ref cursor parameter (supported).

gaussdb=# CREATE OR REPLACE PROCEDURE proc_sys_ref(OUT c1 REFCURSOR)
IS
DECLARE
  PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
 OPEN c1 FOR SELECT section_id FROM sections ORDER BY section_id;

END;
/
CREATE PROCEDURE

gaussdb=# CREATE OR REPLACE PROCEDURE proc_sys_call() AS 
DECLARE
  c1 SYS_REFCURSOR;
  temp NUMBER(4);
BEGIN
  proc_sys_ref(c1);
  IF c1%ISOPEN THEN
    RAISE NOTICE '%','OK';
 END IF;

  LOOP
    FETCH c1 INTO temp;
    RAISE NOTICE '%',c1%ROWCOUNT;
    EXIT WHEN c1%NOTFOUND;
  END LOOP;
END;
/
CREATE PROCEDURE

gaussdb=# CALL proc_sys_call();
NOTICE:  OK
NOTICE:  1
NOTICE:  2
NOTICE:  3
NOTICE:  4
NOTICE:  4
 proc_sys_call 
---------------

(1 row)
gaussdb=# DROP PROCEDURE proc_sys_ref;
DROP PROCEDURE 
gaussdb=# DROP PROCEDURE proc_sys_call;
DROP PROCEDURE

The PROCEDURE IN or INOUT output parameter passes the ref cursor parameter (not supported).

gaussdb=# CREATE OR REPLACE PROCEDURE proc_sys_ref(IN c1 REFCURSOR)
IS
DECLARE
  PRAGMA AUTONOMOUS_TRANSACTION;
  temp NUMBER(4);
BEGIN
  IF c1%ISOPEN THEN
    RAISE NOTICE '%','OK';
  END IF;

  LOOP
    FETCH c1 INTO temp;
    RAISE NOTICE '%',c1%ROWCOUNT;
    EXIT WHEN c1%NOTFOUND;
  END LOOP;
END;
/
CREATE PROCEDURE

gaussdb=# CREATE OR REPLACE PROCEDURE proc_sys_call() AS 
DECLARE
  c1 SYS_REFCURSOR;
  temp NUMBER(4);
BEGIN
  OPEN c1 FOR SELECT section_id FROM sections ORDER BY section_id;
  proc_sys_ref(c1);
END;
/
CREATE PROCEDURE

gaussdb=# CALL proc_sys_call();
ERROR:  Unsupported: ref_cursor parameter is not supported for autonomous transactions.
CONTEXT:  SQL statement "CALL proc_sys_ref(c1)"
PL/pgSQL function proc_sys_call() line 7 at PERFORM
gaussdb=# DROP PROCEDURE proc_sys_ref;
DROP PROCEDURE

The FUNCTION RETURN output parameter passes the ref cursor parameter (not supported).

gaussdb=# DROP PROCEDURE IF EXISTS proc_sys_ref;
gaussdb=# CREATE OR REPLACE FUNCTION proc_sys_ref() RETURN SYS_REFCURSOR IS
DECLARE
  PRAGMA AUTONOMOUS_TRANSACTION;
        c1 SYS_REFCURSOR;
BEGIN
 OPEN c1 FOR SELECT section_id FROM sections ORDER BY section_id;
 return c1;
END;
/
ERROR:  Autonomous function do not support ref cursor as return types or out, inout arguments.
DETAIL:  N/A

The FUNCTION OUT output parameter passes the ref cursor parameter (not supported).

gaussdb=# DROP FUNCTION IF EXISTS proc_sys_ref;
gaussdb=# CREATE OR REPLACE FUNCTION proc_sys_ref(C1 out SYS_REFCURSOR)
gaussdb-# return SYS_REFCURSOR
gaussdb-# IS
gaussdb$# declare
gaussdb$#   PRAGMA AUTONOMOUS_TRANSACTION;
gaussdb$# BEGIN
gaussdb$#  OPEN C1 FOR SELECT section_ID FROM sections ORDER BY section_ID;
gaussdb$#  return 1;
gaussdb$# END;
gaussdb$# /
ERROR:  Autonomous function do not support ref cursor as return types or out, inout arguments.
DETAIL:  N/A

On the client (such as gsql and JDBC), the autonomous transaction PROCEDURE with the output parameter ref cursor is directly called. (Not supported. In this case, cursor data cannot be read.)

gaussdb=# CREATE OR REPLACE PROCEDURE proc_sys_ref(OUT c1 REFCURSOR)
IS
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
OPEN c1 FOR SELECT section_id FROM sections ORDER BY section_id;
END;
/
CREATE PROCEDURE
gaussdb=# begin;
BEGIN
gaussdb=# call proc_sys_ref(null);
         c1
--------------------
 <unnamed portal 1>
(1 row)

gaussdb=# fetch "<unnamed portal 1>";
ERROR:  cursor "<unnamed portal 1>" does not exist
gaussdb=# end;
ROLLBACK
gaussdb=# DROP PROCEDURE proc_sys_ref;
DROP PROCEDURE
-- Drop the table.
gaussdb=# DROP TABLE sections;
DROP TABLE

The autonomous transaction function cannot directly return the record type or the out output parameter and the record type at the same time.

gaussdb=# CREATE TABLE test_in (id INT,a DATE);
CREATE TABLE

gaussdb=# CREATE OR REPLACE FUNCTION autonomous_out()
RETURNS RECORD
LANGUAGE PLPGSQL AS $$
DECLARE PRAGMA AUTONOMOUS_TRANSACTION;
         r1 RECORD;
BEGIN
    DBE_OUTPUT.PRINT_LINE('THIS IS IN AUTONOMOUS_F_139_7');
    TRUNCATE test_in;
    INSERT INTO test_in VALUES (1,'1909-01-01');
    SELECT * INTO r1 FROM test_in;
RETURN r1;
END;
$$;
CREATE FUNCTION

gaussdb=# SELECT ok.id,ok.a FROM autonomous_out() AS ok(id INT,a DATE);
ERROR:  unrecognized return type for PLSQL function.

gaussdb=# CREATE TYPE rec IS (e1 INTEGER, e2 VARCHAR2);
CREATE TYPE
gaussdb=# CREATE OR REPLACE FUNCTION func(ele3 INOUT VARCHAR2) RETURN rec AS
i INTEGER;
ele1 rec;
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
NULL;
RETURN ele1;
END;
/
CREATE FUNCTION

gaussdb=# CALL func(1);
 e1 | e2 
----+----
    | 
(1 row)

gaussdb=# DROP TABLE test_in;
DROP TABLE
gaussdb=# DROP FUNCTION autonomous_out;
DROP FUNCTION 
gaussdb=# DROP FUNCTION func;
DROP FUNCTION

The isolation level of an autonomous transaction cannot be changed.

gaussdb=# CREATE OR REPLACE PROCEDURE auto_func(r INT)
AS
DECLARE
  a INT;
  PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
 a:=r;
END;
/
CREATE PROCEDURE
gaussdb=# call auto_func(1);
ERROR:  ERROR:  SET TRANSACTION ISOLATION LEVEL must be called before any query
CONTEXT:  SQL statement "SET TRANSACTION ISOLATION LEVEL SERIALIZABLE"
PL/pgSQL function auto_func(integer) line 6 at SQL statement
referenced column: auto_func
gaussdb=# DROP FUNCTION auto_func;
DROP FUNCTION

Autonomous transactions do not support the setof return type.

gaussdb=# CREATE TABLE test_in (id INT,a DATE);
CREATE TABLE
gaussdb=# CREATE TABLE test_main (id INT,a DATE);
CREATE TABLE
gaussdb=# INSERT INTO test_main VALUES (1111,'2021-01-01'),(2222,'2021-02-02');
INSERT 0 2
gaussdb=# TRUNCATE test_in,test_main;
TRUNCATE TABLE
gaussdb=# CREATE OR REPLACE FUNCTION autonomous_f_022(num1  INT) RETURNS SETOF test_in
LANGUAGE PLPGSQL AS $$
DECLARE
count INT :=3;
test_row test_in%ROWTYPE;
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
    WHILE TRUE
    LOOP
    IF count=3 THEN
    NULL;
    ELSE 
    IF count=2 THEN
        INSERT INTO test_main VALUES (count,'2021-03-03');
        GOTO pos1;
    END IF;                
    END IF;
    count=count-1;
    END LOOP;
    INSERT INTO test_main VALUES (1000,'2021-04-04');
     <<pos1>>
     FOR test_row IN SELECT * FROM test_main
     LOOP
        RETURN NEXT test_row;
       END LOOP;
      RETURN;
END;
$$;
ERROR:  Autonomous transactions do not support RETURN SETOF.
DETAIL:  N/A

gaussdb=# DROP TABLE test_main;
DROP TABLE
gaussdb=# DROP TABLE test_in;
DROP TABLE

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