Bug in my code or strange memory behavior ?

Question

Hi, Guys !
It's been a while since I post something in this forum - trying to use your help when it's really needed.
So, here we go ...
(we use Oracle 8.1.7 on Unix box and SQL * Plus 8.1.6)
While back I wrote "core" PL/SQL package that resides in let's say DB1 database. It has RECORD_EXISTS_FNC function designed to dynamically check If the record exists in certain table/view. Assumptions are that you pass in :
Table/View name, Column name, and unique numeric value (because by DBA rules all of our Tables have SEQUENCE as a Primary Key. And I plan soon to put in overloaded function to accept unique character value)
Also every Table has SYS_TIME_STAMP and SYS_UPDATE_SEQuence columns that populated by Trigger before Insert/Update representing Last Update time_stamp
and how many times record was updated within same second.
(in case more than one User updates same record in same time - that was written before Oracle had more granular date/time). So function has SYS_TIME_STAMP and SYS_UPDATE_SEQUENCE parameters (optional) accordingly.
And It looks something like :
FUNCTION RECORD_EXISTS_FNC
(iBV_NAME IN USER_VIEWS.VIEW_NAME%TYPE,
iPK_FIELD IN USER_TAB_COLUMNS.COLUMN_NAME%TYPE,
iPK_VALUE IN NUMBER,
iSYS_TIME_STAMP IN DATE DEFAULT NULL,
iSYS_UPDATE_SEQ IN NUMBER DEFAULT NULL) RETURN BOOLEAN IS
TYPE REF_CUR IS REF CURSOR;
CR REF_CUR;
i PLS_INTEGER DEFAULT 0;
vRESULT BOOLEAN DEFAULT FALSE;
vQUERY USER_SOURCE.TEXT%TYPE;
BEGIN
vQUERY := 'SELECT 1 FROM ' || iBV_NAME || ' WHERE ' || iPK_FIELD || ' = ' || iPK_VALUE;
IF iSYS_TIME_STAMP IS NOT NULL AND iSYS_UPDATE_SEQ IS NOT NULL THEN
vQUERY := vQUERY || ' AND SYS_TIME_STAMP = TO_DATE (''' || iSYS_TIME_STAMP || ''')
AND SYS_UPDATE_SEQ = ' || iSYS_UPDATE_SEQ;
END IF;
IF iBV_NAME IS NOT NULL AND
iPK_FIELD IS NOT NULL AND
iPK_VALUE IS NOT NULL THEN
OPEN CR FOR vQUERY;
FETCH CR INTO i;
vRESULT := CR%FOUND;
CLOSE CR;
END IF;
RETURN vRESULT;
EXCEPTION
WHEN OTHERS THEN
IF CR%ISOPEN THEN
CLOSE CR;
END IF;
INSERT_ERROR_LOG_PRC ('CORE_PKG', 'ORACLE', SQLCODE, SQLERRM, 'RECORD_EXISTS_FNC');
RETURN vRESULT;
END RECORD_EXISTS_FNC;
So the problem is when I call this function from let's say
database DB2 (via db remote link and synonym) and I know exactly that record does exists (because I am selecting those SYS fields before pass them in) - I get the correct result TRUE. The other programmer (Patrick) calls this function within same DB2 database, within same UserID/password (obviously different session), running exactly the same testing code and gets result FALSE (record doesn't exist, but it does !) He tried to Logoff/Login again several times within several days and try to run it and still was getting FALSE !
I tried to Logoff/Login again and I was getting mostly TRUE and sometimes FALSE too !!!
I thought may be It has something to do with REF CURSOR that I use to build SQL on the fly, so I changed to NDS
using EXECUTE IMMEDIATE statement - nothing changed.
vQUERY := 'SELECT COUNT (1) FROM ' || iBV_NAME || ' WHERE ' || iPK_FIELD || ' = ' || iPK_VALUE;
IF iSYS_TIME_STAMP IS NOT NULL AND iSYS_UPDATE_SEQ IS NOT NULL THEN
vQUERY := vQUERY || ' AND SYS_TIME_STAMP = TO_DATE (''' || iSYS_TIME_STAMP || ''') AND SYS_UPDATE_SEQ = ' || iSYS_UPDATE_SEQ;
END IF;
EXECUTE IMMEDIATE vQUERY INTO i;
vRESULT := NOT (i = 0);
RETURN vRESULT;
Interesting note : when Patrick doesn't pass SYS parameters (Time_stamp, Update_sequence), or passes NULLs - function always finds the record ! (Statement 2 below)
May be it has to do with the way TO_DATE () function gets parsed in that dynamic SQL - I don't know ...
Here's the test code :
SET SERVEROUTPUT ON;
DECLARE
SYS_TIME DATE;
SYS_SEQ NUMBER;
bEXISTS BOOLEAN DEFAULT FALSE;
BEGIN
SELECT SYS_TIME_STAMP, SYS_UPDATE_SEQ INTO SYS_TIME, SYS_SEQ FROM LOCATION_BV WHERE PK = 1;
bEXISTS := CORE_PKG.RECORD_EXISTS_FNC ('LOCATION_BV','PK',1, SYS_TIME, SYS_SEQ); -- STATEMENT 1
--bEXISTS := CORE_PKG.RECORD_EXISTS_FNC ('LOCATION_BV','PK',1, NULL, NULL);        -- STATEMENT 2
IF bEXISTS THEN
DBMS_OUTPUT.PUT_LINE ('TRUE');
ELSE
DBMS_OUTPUT.PUT_LINE ('FALSE');
END IF;
END;
I asked our DBA, he has no clue about this strange inconsistent results.
I debugged line by line, extracted that generated SQL and ran it in same account - works fine !
Does anyone knows or have clues or can help what's going on ???
I don't know If this is bug in my code or strange memory behavior ?
(Please let me know If anything unclear)
Thanx a lot for your help and time !
Steve K.

Answer 1

see your other thread
Bug in my code or strange memory behavior ?