ORA-01460: unimplemented or unreasonable error & OPEN-FOR statement ...

Question

Hi,
I have a procedure that opens a cursor which returns a result set based on a dynamic SELECT statement. The IN clause
in most cases needs to handle more than 1000 expressions. So to avoid the ORA-01785 error, I use a function to
convert the comma separated list of ids (which are unknown) into a collection which can then be used in the sub query
to process each expression or id. I assumed that the maximum string length I could use for these list of ids was
32767, i.e. VARCHAR2. But f I attempt to open the cursor with a list of ids where the string length is greater than 4000 bytes , the cursor is invalid
and it seems to throw the following Oracle error:
ORA-01460: unimplemented or unreasonable conversion ...
Note that anything less than 4000 bytes is fine. I have attached some of the code below and would appreciate if anyone
could tell me what im doing wrong! For example, can a varchar2 variable greater than 4000 bytes not be used when
executing dynamic SQL in the context of the OPEN-FOR statement?
-- Create type to hold collection of identifiers.
CREATE OR REPLACE TYPE IDList IS TABLE OF NUMBER;
-- Function which converts a string of comma separated list of identifiers
-- into a collection.
CREATE OR REPLACE FUNCTION fnConvertIDListToCollection(
     varList IN VARCHAR2,
     varDelimiter IN VARCHAR2 DEFAULT ',')
RETURN IDList
IS
     varString long := varList || varDelimiter;
     varPos pls_integer;
     varData IDList := IDList();
BEGIN
     LOOP
          varPos := instr(varString, varDelimiter);
          EXIT WHEN (nvl(varPos, 0) = 0);
          varData.extend;
          varData(varData.count) := trim(substr(varString, 1, varPos - 1));
          varString := substr(varString, varPos + 1);
     END LOOP;
     RETURN (varData);
END;
CREATE OR REPLACE PROCEDURE MyTestProc
myCursor OUT SYS_REFCURSOR
AS
varListOfIds VARCHAR2(32767);
BEGIN
     -- Hard coding this for now but this will be an incoming parameter containing a list
     -- of unknown ids, separated with commas.
     varListOfIds := '1,2 .. , 5000';
     OPEN myCursor FOR
     'SELECT     DISTINCT val1, val2, val3
     FROM TABLEA
     WHERE     val1 IN (select * from table(cast(fnConvertIDListToCollection(:ListOfIds) as IDList)))' USING varListOfIds;
END;
/

Answer 1

APC,
Many thanks for the suggestion and yes I could possibly implement an alternative solution, certainly for some cases but I need to investigate further for others. I'm migrating some SQL Server logic over to Oracle and that was simply the approach taken on that platform.
Could I trouble you with one further question as a newbie to all of this. I hinted in my last response that I was somewhat confused over the limits with the use of varchar2 variables in PL/SQL. If I were building up a piece of dynamic SQL (e.g. SELECT statement including a WHERE clause) using an incoming VARCHAR2 parameter for the WHERE clause, can this parameter contain more than 4000 bytes if necessary. I assumed it could be as big as 32767 bytes but an earlier response suggested a maximum of 4000 bytes. Really sorry for probably a fairly basic Oracle question but it would be very appreciated if you could explain this to me.
Again, many thanks.