引用游标在XMLType.createxml中丢失

Question

我正在调用一个返回引用游标的函数,我XMLType.createxml用来将结果转换为XML,例如

select XMLType.createxml(package_name.storedProcName('PARAM1', 'PARAM2', 'PARAM3')) as sresult from dual;

但是,我发现这有一个不受欢迎的副作用.似乎用于检索XMLType数据的游标永远不会关闭.使用这种技术多次调用函数后,我总是遇到以下错误:

ORA-01000: maximum open cursors exceeded

我没有光标的句柄,因此我无法手动关闭它.此外,我们使用池化连接,因此没有连接重置可以自动释放这些游标.关于这个还能做什么？

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这是我的Oracle版本(从v $版本返回):

Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi
PL/SQL Release 10.2.0.5.0 - Production                          
CORE    10.2.0.5.0  Production                                      
TNS for HPUX: Version 10.2.0.5.0 - Production                   
NLSRTL Version 10.2.0.5.0 - Production

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(对于那些感兴趣的人,这里是我之前关于XMLType的问题的链接.)

Answer 1

似乎有一个错误,您应该向Oracle支持打开服务请求.我将发布一个测试用例,在9i和11.2.0.3中重现你的发现:

SQL> SHOW parameter open_cursors

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
open_cursors                         integer     600

SQL> CREATE OR REPLACE FUNCTION ret_cursor RETURN SYS_REFCURSOR IS
  2     l SYS_REFCURSOR;
  3  BEGIN
  4     OPEN l FOR
  5        SELECT * FROM dual;
  6     RETURN l;
  7  END;
  8  /

Function created

使用上述函数调用时,XMLType不会正确关闭游标,而它与静态SQL一起使用时效果很好:

SQL> /* Works as expected with static cursor */
  2  DECLARE
  3     l XMLTYPE;
  4  BEGIN
  5     FOR i IN 1 .. 1e4 LOOP
  6        SELECT xmltype.createXML(CURSOR(SELECT * FROM DUAL)) INTO l FROM dual;
  7     END LOOP;
  8  END;
  9  /      

PL/SQL procedure successfully completed

SQL> /* Fails with call to dynamic cursor */
SQL> DECLARE
  2     l XMLTYPE;
  3  BEGIN
  4     FOR i IN 1 .. 1e4 LOOP
  5        SELECT xmltype.createXML(ret_cursor) INTO l FROM dual;
  6     END LOOP;
  7  END;
  8  /
DECLARE
*
ERROR at line 1:
ORA-01000: maximum open cursors exceeded
ORA-06512: at "APPS.RET_CURSOR", line 4
ORA-06512: at line 5

您应该能够使用包装函数来防止ORA-01000发生(在9iR2,11gR2上测试):

SQL> CREATE OR REPLACE FUNCTION wrap_xml(p SYS_REFCURSOR) RETURN XMLTYPE IS
  2     l XMLTYPE;
  3  BEGIN
  4     l := xmltype.CreateXML(p);
  5     IF p%ISOPEN THEN
  6        CLOSE p;
  7     END IF;
  8     RETURN l;
  9  END;
 10  /

Function created

SQL> DECLARE
  2     l XMLTYPE;
  3  BEGIN
  4     FOR i IN 1 .. 1e4 LOOP
  5        l := wrap_xml(ret_cursor); -- a SELECT FROM dual will still fail here
  6                                   -- on 9i but not on 11g 
  7     END LOOP;
  8  END;
  9  /

PL/SQL procedure successfully completed