oracle管道函數的用法
oracle管道函數是一類特殊的函數，oracle管道函數返回值類型必須為集合，下面就為您將介紹oracle管道函數的語法，供您參考學習。
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后一次性的返回給客戶端。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oracle9i以后可以使用管道函數(pipeline function)。
關鍵字PIPELINED表明這是一個oracle管道函數，oracle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，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 8create 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oracle9205及其之后的版本中，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
這是由于在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 升級到之后的版本，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ORA-1002錯誤。
ALTER SYSTEM SET EVENT = "10946 trace name context forever, level 8" scope=spfile;
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