oracle – 如何使用CLOB调用REPLACE(不超过32K)

Oracle 11g肯定提高了CLOB的可用性,使大多数字符串函数重载,因此它们现在可以与CLOB本机一起工作.

但是,一位同事从他的代码中得到了这个错误：

ORA-22828: input pattern or replacement parameters exceed 32K size limit
22828. 00000 -  "input pattern or replacement parameters exceed 32K size limit"
*Cause:    Value provided for the pattern or replacement string in the form of
           VARCHAR2 or CLOB for LOB sql functions exceeded the 32K size limit.
*Action:   Use a shorter pattern or process a long pattern string in multiple
           passes.

仅当要替换的第三个参数是具有超过32k字符的CLOB时才会发生这种情况.

(Oracle Database 11g企业版11.2.0.3.0版 – 64位生产)

测试用例：

declare
  v2 varchar2(32767);
  cl_small clob;
  cl_big clob;
  cl_big2 clob;
begin
  v2 := rpad('x',32767,'x');
  dbms_output.put_line('v2:' || length(v2));
  cl_small := v2;
  dbms_output.put_line('cl_small:' || length(cl_small));
  cl_big := v2 || 'y' || v2;
  dbms_output.put_line('cl_big[1]:' || length(cl_big));
  cl_big2 := replace(cl_big,'y',cl_small);
  dbms_output.put_line('cl_big[2]:' || length(cl_big2));
  cl_big2 := replace(cl_big,cl_big); 
  dbms_output.put_line('cl_big[3]:' || length(cl_big2));
end;
/

结果：

v2:32767
cl_small:32767
cl_big[1]:65535
cl_big[2]:98301
ORA-22828: input pattern or replacement parameters exceed 32K size limit

这似乎与暗示替换字符串可能是CLOB的文档不一致 – 我认为这应该意味着任何CLOB都将被允许,而不仅仅是那些恰好是< 32K：http://docs.oracle.com/cd/E11882_01/server.112/e41084/functions153.htm#SQLRF00697

这是一个功能粗略的初稿,它将在某些限制下完成工作,但尚未经过很好的测试：

function replace_with_clob
  (i_source in clob,i_search in varchar2,i_replace in clob
  ) return clob is
  l_pos pls_integer;
begin
  l_pos := instr(i_source,i_search);
  if l_pos > 0 then
    return substr(i_source,1,l_pos-1)
        || i_replace
        || substr(i_source,l_pos+length(i_search));
  end if;
  return i_source;
end replace_with_clob;

它只对搜索词的第一个实例进行单个替换.

declare
  v2 varchar2(32767);
  cl_small clob;
  cl_big clob;
  cl_big2 clob;
begin
  v2 := rpad('x',cl_small);
  dbms_output.put_line('cl_big[2]:' || length(cl_big2));
  cl_big2 := replace_with_clob(cl_big,cl_big); 
  dbms_output.put_line('cl_big[3]:' || length(cl_big2));
end;
/

v2:32767
cl_small:32767
cl_big[1]:65535
cl_big[2]:98301
cl_big[3]:131069