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，在普通的函數中，使用dbms_output輸出的信息，需要在服務器執行完整個函數後一次性的返回給客戶端。但你如果需要在客戶端實時的輸出函數執行過程中的一些信息，在Oracle 9i以後則可以使用管道函數(pipeline function)。
PIPELINED（關鍵字）表明這是一個管道函數，管道函數的返回值類型必須為集合，在函數中，PIPE ROW語句被用來返回該集合的單個元素，函數則以一個空的RETURN語句結束，以表明它已經完成。
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中執行該函數，大家需要首先設置arraysize為1，否則服務器會按照默認的15來向客戶端返回信息，這會影響我們的測試效果。
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中執行DML操作，則必須使用自治事務，否則會報ORA-14551錯誤
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及其之後的版本中，在pipeline function中使用自治事務，則必須在pipe row之前提交或者回滾事務，否則會報ORA-06519錯誤。
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
此處是由於在9205中修復Bug 2711518導致了自治事務的行為有所改變。如果系統從9205之前的版本升級到之後的版本，需要保證pipeline function的行為和以前版本一致，Oracle提供了一個10946事件來設置和以前版本的兼容性，如果在管道函數中使用了select for update的cursor，則必須設置event回歸以前的特性，否則即使在pipe row之前commit也會導致出現ORA-1002錯誤。
ALTER SYSTEM SET EVENT = "10946 trace name context forever, level 8" scope=spfile;
