Updated on 2024-05-07 GMT+08:00

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);
    NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using 'id1' 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 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);
    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=# 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
  • Autonomous transactions do not support ref_cursor parameter transfer.
    gaussdb=# create table sections(section_ID int);
    gaussdb=# insert into sections values(1);
    gaussdb=# insert into sections values(1);
    gaussdb=# insert into sections values(1);
    gaussdb=# insert into sections values(1);
    
    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
    gaussdb=# CREATE OR REPLACE function proc_sys_ref(OUT C2 SYS_REFCURSOR, OUT a int)
    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
  • Distributed autonomous transactions of the IMMUTABLE and STABLE types cannot be pushed down.
    gaussdb=# CREATE OR REPLACE PROCEDURE autonomous_test_in_p_116(num1 INT ) 
    IMMUTABLE 
    AS
    DECLARE
    PRAGMA AUTONOMOUS_TRANSACTION;
    BEGIN
    PERFORM pg_sleep(1);
    END;
    /
    ERROR:  Autonomous transactions do not support STABLE/IMMUTABLE.
    DETAIL:  Please remove stable/immutable.
    
    gaussdb=# CREATE OR REPLACE PROCEDURE autonomous_test_in_p_117(num1 INT ) STABLE AS
    DECLARE
    PRAGMA AUTONOMOUS_TRANSACTION;
    BEGIN
    PERFORM pg_sleep(1);
    END;
    /
    ERROR:  Autonomous transactions do not support STABLE/IMMUTABLE.
    DETAIL:  Please remove stable/immutable.
  • The distributed system does not support detection. When a deadlock occurs, a lock waiting timeout error is reported.
    gaussdb=# CREATE TABLE test_lock (id INT,a DATE);
    NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using 'id' as the distribution column by default.
    HINT:  Please use 'DISTRIBUTE BY' clause to specify suitable data distribution column.
    CREATE TABLE
    gaussdb=# INSERT INTO test_lock VALUES (10,SYSDATE),(11,SYSDATE),(12,SYSDATE);
    INSERT 0 3
    gaussdb=# CREATE OR REPLACE FUNCTION autonomous_test_lock(num1 INT,num2 INT) RETURNS
    INTEGER LANGUAGE plpgsql AS $$
    DECLARE num3 INT := 4;
    PRAGMA AUTONOMOUS_TRANSACTION;
    BEGIN
    UPDATE test_lock SET a=SYSDATE WHERE id =11;
    RETURN num1+num2+num3;
    END;
    $$;
    CREATE FUNCTION
    
    gaussdb=# START TRANSACTION;
    START TRANSACTION
    gaussdb=# UPDATE test_lock SET a=SYSDATE WHERE id =11;
    UPDATE 1
    gaussdb=# CALL autonomous_test_lock(1,1);
    ERROR:  ERROR:  Lock wait timeout: thread 139874535470848 on node datanode1 waiting for ShareLock on transaction 16214 after 120000.124 ms
    DETAIL:  blocked by hold lock thread 139874577413888, statement <UPDATE test_lock SET a = "sysdate"() WHERE id =11;>, hold lockmode ExclusiveLock.
    CONTEXT:  SQL statement "UPDATE test_lock SET a=SYSDATE WHERE id =11"
    PL/SQL function autonomous_test_lock(integer,integer) line 5 at SQL statement
    referenced column: autonomous_test_lock
    
    gaussdb=# END;
    ROLLBACK
    gaussdb=# DROP TABLE test_lock;
    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 OR REPLACE FUNCTION auto_func() RETURN RECORD
    AS
    DECLARE
      TYPE rec_type IS RECORD(c1 INT, c2 INT);
      r rec_type;
      PRAGMA AUTONOMOUS_TRANSACTION;
    BEGIN
      r.c1:=101;
      r.c2:=201;
      RETURN r;
    END;
    /
    CREATE FUNCTION
    
    gaussdb=# SELECT auto_func();
    ERROR:  unrecognized return type for PLSQL function.
    CONTEXT:  referenced column: auto_func
  • 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 FUNCTION
    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/SQL function auto_func(integer) line 6 at SQL statement
    referenced column: auto_func
  • Autonomous transactions do not support the setof return type.
    gaussdb=# CREATE OR REPLACE FUNCTION test_set() RETURN SETOF INT
    AS
    DECLARE
    PRAGMA AUTONOMOUS_TRANSACTION;
    BEGIN
        RETURN QUERY (SELECT unnest(ARRAY[ARRAY[1, 2], ARRAY[3, 4]]));
    END;
    /
    ERROR:  Autonomous transactions do not support RETURN SETOF.
    DETAIL:  N/A