转:Oracle如何使用pipeline function获得实时输出

如何使用pipeline function获得实时输出

create type lookup_row as

  record ( idx number, text varchar2(20) );

create type lookups_tab as table of lookup_row;

create or replace function Lookups_Fn

  return lookups_tab

  pipelined

is

  v_row lookup_row;

begin

  for j in 1..10

  loop

    v_row :=

      case j

        when 1 then lookup_row ( 1, 'one' )

        when 2 then lookup_row ( 2, 'TWO' )

        when 3 then lookup_row ( 3, 'three' )

        when 4 then lookup_row ( 4, 'FOUR' )

        when 5 then lookup_row ( 5, 'five' )

        when 6 then lookup_row ( 6, 'SIX' )

        when 7 then lookup_row ( 7, 'seven' )

        else        lookup_row ( j, 'other' )

      end;

    pipe row ( v_row );

  end loop;

  return;

end Lookups_Fn;

很多人都知道，在普通的函数中，使用dbms_output输出的信息，需要在服务器执行完整个函数后一次性的返回给客户端。但你如果需要在客户端实时的输出函数执行过程中的一些信息，在Oracle 9i以后则可以使用管道函数(pipeline function)。

PIPELINED（关键字）表明这是一个管道函数，管道函数的返回值类型必须为集合，在函数中，PIPE ROW语句被用来返回该集合的单个元素，函数则以一个空的RETURN语句结束，以表明它已经完成。

create or replace type MsgType as table of varchar2(4000);

/

create or replace function f_pipeline_test

return MsgType

PIPELINED

as

begin

    for i in 1 .. 10

    loop

        pipe row( 'Iteration ' || i || ' at ' || systimestamp );

        dbms_lock.sleep(1);

    end loop;

    pipe row( 'All done!' );

    return;

end;

/

在sql*plus中执行该函数，大家需要首先设置arraysize为1，否则服务器会按照默认的15来向客户端返回信息，这会影响我们的测试效果。

SQL> set arraysize 1

SQL> select * from table( f_pipeline_test );

COLUMN_VALUE

-----------------------------------------------------

Iteration 1 at 14-FEB-08 02.13.18.273988000 PM +08:00

Iteration 2 at 14-FEB-08 02.13.19.275988000 PM +08:00

Iteration 3 at 14-FEB-08 02.13.20.277767000 PM +08:00

Iteration 4 at 14-FEB-08 02.13.21.279591000 PM +08:00

Iteration 5 at 14-FEB-08 02.13.22.281366000 PM +08:00

Iteration 6 at 14-FEB-08 02.13.23.283189000 PM +08:00

Iteration 7 at 14-FEB-08 02.13.24.283965000 PM +08:00

Iteration 8 at 14-FEB-08 02.13.25.285785000 PM +08:00

Iteration 9 at 14-FEB-08 02.13.26.286570000 PM +08:00

Iteration 10 at 14-FEB-08 02.13.27.288387000 PM +08:00

All done!

11 rows selected.

如果要在pipeline中执行DML操作，则必须使用自治事务，否则会报ORA-14551错误

create or replace function f_pipeline_testdml

return MsgType

PIPELINED

as

begin

    for i in 1 .. 10

    loop

        insert into test values(1);

        pipe row( 'insert into test values( ' || i || ') success at ' || systimestamp );

        dbms_lock.sleep(1);

    end loop;

    pipe row( 'All done!' );

    return;

end;

/

SQL>  select * from table( f_pipeline_testdml );

 select * from table( f_pipeline_testdml )

                      *

ERROR at line 1:

ORA-14551: cannot perform a DML operation inside a query

ORA-06512: at "NING.F_PIPELINE_TESTDML", line 8

create or replace function f_pipeline_testdml

return MsgType

PIPELINED

as

pragma autonomous_transaction;

begin

for i in 1 .. 10

loop

insert into test values(1);

commit;

pipe row( 'insert values ' || i || ' success at ' || systimestamp );

dbms_lock.sleep(1);

end loop;

pipe row( 'All done!' );

return;

end;

/

SQL> select * from table( f_pipeline_testdml );

COLUMN_VALUE

--------------------------------------------------------------------------------

insert values  1  success at 14-FEB-08 02.16.47.855158000 PM +08:00

insert values  2  success at 14-FEB-08 02.16.48.865559000 PM +08:00

insert values  3  success at 14-FEB-08 02.16.49.867377000 PM +08:00

insert values  4  success at 14-FEB-08 02.16.50.873154000 PM +08:00

insert values  5  success at 14-FEB-08 02.16.51.874942000 PM +08:00

insert values  6  success at 14-FEB-08 02.16.52.880781000 PM +08:00

insert values  7  success at 14-FEB-08 02.16.53.882543000 PM +08:00

insert values  8  success at 14-FEB-08 02.16.54.894348000 PM +08:00

insert values  9  success at 14-FEB-08 02.16.55.896153000 PM +08:00

insert values  10 success at 14-FEB-08 02.16.56.901904000 PM +08:00

All done!

11 rows selected.

在Oracle 9205及其之后的版本中，在pipeline function中使用自治事务，则必须在pipe row之前提交或者回滚事务，否则会报ORA-06519错误。

create or replace function f_pipeline_testdml

return MsgType

PIPELINED

as

pragma autonomous_transaction;

begin

for i in 1 .. 10

loop

insert into test values(1);

pipe row( 'insert values ' || i || ' success at ' || systimestamp );

dbms_lock.sleep(1);

end loop;

pipe row( 'All done!' );

commit;

return;

end;

/

SQL> select * from table( f_pipeline_testdml );

select * from table( f_pipeline_testdml )

                     *

ERROR at line 1:

ORA-06519: active autonomous transaction detected and rolled back

ORA-06512: at "NING.F_PIPELINE_TESTDML", line 10

此处是由于在9205中修复Bug 2711518导致了自治事务的行为有所改变。如果系统从9205之前的版本升级到之后的版本，需要保证pipeline function的行为和以前版本一致，Oracle提供了一个10946事件来设置和以前版本的兼容性，如果在管道函数中使用了select for update的cursor，则必须设置event回归以前的特性，否则即使在pipe row之前commit也会导致出现ORA-1002错误。

ALTER SYSTEM SET EVENT = "10946 trace name context forever, level 8" scope=spfile;