SELECT INTO not working as expected in procedure - oracle

Question

Please, advice me on below procedure. below query returns null on filename_ but not sure how to get this filename_ properly.
PROCEDURE pickup( app_id IN VARCHAR2, Interval IN NUMBER, filename_ OUT VARCHAR2, status_ OUT VARCHAR2) IS
BEGIN
SELECT filename, status INTO filename_, status_
FROM (SELECT filename, status, CUSTPROFID, FILESIZE, AMP_FILE_NAME FROM INBOUND_UNCOMPLETED_PROCESS WHERE (status = 'error' or status = 'retry')
AND application_id IS NULL AND CREATEDAT < sysdate - 1/(24*60) AND (LAST_UPDATEDAT IS NULL OR LAST_UPDATEDAT < sysdate - Interval/(24*60))
order by LAST_UPDATEDAT NULLS FIRST)
WHERE ROWNUM < 2 FOR UPDATE NOWAIT;
UPDATE INBOUND SET application_id = app_id WHERE filename = filename_;
COMMIT;
EXCEPTION
WHEN NO_DATA_FOUND THEN
filename_ := NO_DATA_FOUND;
WHEN OTHERS THEN
filename_ := NULL;
END pickup;
Below query returns filename_ and status_ but I would need to add ORDER BY LAST_UPDATEDAT on the select query.
PROCEDURE pickup( app_id IN VARCHAR2, Interval IN NUMBER, filename_ OUT VARCHAR2, status_ OUT VARCHAR2) IS
BEGIN
SELECT filename, status INTO filename_, status_
FROM INBOUND WHERE (status = 'error' or status = 'retry')
AND application_id IS NULL AND CREATEDAT < sysdate - 1/(24*60) AND (LAST_UPDATEDAT IS NULL OR LAST_UPDATEDAT < sysdate - Interval/(24*60))
AND ROWNUM < 2 FOR UPDATE NOWAIT;
UPDATE INBOUND SET application_id = app_id WHERE filename = filename_;
COMMIT;
EXCEPTION
WHEN NO_DATA_FOUND THEN
filename_ := NO_DATA_FOUND;
WHEN OTHERS THEN
filename_ := NULL;
END pickup;
Thank you!

Answer 1

There are two errors in the procedure.
In your NO_DATA_FOUND exception handler, the line:
filename_ := NO_DATA_FOUND;
is not valid as NO_DATA_FOUND is a built-in exception and not a string. You need to change this to something like:
filename_ := 'Not found';
When you fix this then it the SELECT statement raises the exception:
ORA-02014: cannot select FOR UPDATE from view with DISTINCT, GROUP BY
This is because you can't filter by ROWNUM (or use the modern FETCH FIRST ROW ONLY syntax) alongside FOR UPDATE. This issue is addressed in this answer.
The exception is then caught by the OTHERS handler and NULL is returned.
It is bad practice to catch OTHERS. As you have found there can be many issues and catching OTHERS masks them and makes it difficult to find where the problem lies. If you need to catch exceptions then make sure you are specific about which ones need catching and then any other that gets raised is an error and should cause your code to fail and this gives you the opportunity to debug.
Similarly, using COMMIT should not be used a procedure as it prevents you grouping procedures together and issuing a ROLLBACK command to revert multiple changes at once. Instead, the block calling the procedure should COMMIT the values once all changes have been made.
The solution is to do something like this:
CREATE PACKAGE pkg_name IS
PROCEDURE pickup(
app_id IN INBOUND.APPLICATION_ID%TYPE,
Interval IN NUMBER,
filename_ OUT INBOUND.FILENAME%TYPE,
status_ OUT INBOUND.STATUS%TYPE
);
END;
/
CREATE PACKAGE BODY pkg_name IS
PROCEDURE pickup(
app_id IN INBOUND.APPLICATION_ID%TYPE,
Interval IN NUMBER,
filename_ OUT INBOUND.FILENAME%TYPE,
status_ OUT INBOUND.STATUS%TYPE
) IS
BEGIN
SELECT filename, status
INTO filename_, status_
FROM INBOUND
WHERE ROWID IN (
SELECT ROWID
FROM INBOUND
WHERE status IN ( 'error', 'retry')
AND application_id IS NULL
AND CREATEDAT < sysdate - 1/(24*60)
AND (LAST_UPDATEDAT IS NULL OR LAST_UPDATEDAT < sysdate - Interval/(24*60))
ORDER BY LAST_UPDATEDAT NULLS FIRST
FETCH FIRST ROW ONLY
)
FOR UPDATE NOWAIT;
UPDATE INBOUND SET application_id = app_id WHERE filename = filename_;
EXCEPTION
WHEN NO_DATA_FOUND THEN
filename_ := 'Not found.';
END pickup;
END;
/
Which, for the sample data:
CREATE TABLE inbound (
application_id VARCHAR2(20),
filename VARCHAR2(20),
status VARCHAR2(20),
CREATEDAT DATE,
LAST_UPDATEDAT DATE
);
INSERT INTO inbound ( filename, status, CREATEDAT, LAST_UPDATEDAT )
SELECT 'abc', 'error', SYSDATE - INTERVAL '3' HOUR, NULL FROM DUAL UNION ALL
SELECT 'def', 'retry', SYSDATE - INTERVAL '2' HOUR, SYSDATE FROM DUAL;
Then:
DECLARE
fn INBOUND.FILENAME%TYPE;
st INBOUND.STATUS%TYPE;
BEGIN
pkg_name.pickup(
app_id => 'E42',
interval => 0,
filename_ => fn,
status_ => st
);
COMMIT;
DBMS_OUTPUT.PUT_LINE( fn || ', ' || st );
END;
/
Outputs:
abc, error
and:
SELECT * FROM inbound;
outputs:
APPLICATION_ID | FILENAME | STATUS | CREATEDAT | LAST_UPDATEDAT
:------------- | :------- | :----- | :-------- | :-------------
E42 | abc | error | 21-OCT-20 | null
null | def | retry | 21-OCT-20 | 21-OCT-20
db<>fiddle here