PostGreSQL - Controlling transactions - postgresql

Question

I have a Stored Procedure that in turns calls several other Stored Procedures; each of them returns true or false and internally deal with errors by store them into a table.
Something like this:
-- (MAIN STORED PROCEDURE)
BEGIN
CALL STORED_PROC_1('WW','TT','FF',result);
IF result = TRUE then
CALL STORED_PROC_2('a','b','c',result);
...
END IF;
END;
IF result != TRUE THEN
ROLLBACK;
ELSE
COMMIT;
END IF;
-- (END MAIN STORED PROCEDURE)
-------
--Example of Stored Procedure 1
CREATE OR REPLACE PROCEDURE STORED_PROC_1 (IN a TEXT, IN b TEXT, IN c TEXT, INOUT result boolean)
AS $BODY$
BEGIN
-- DO SOME STUFF HERE
IF ERROR_FOUND THEN
INSERT INTO ERROR_LOG VALUES ('Error','Type of Error',CURRENT_DATE);
--COMMIT; (I cannot do this commit here but I would like to save the information going into the ERROR_LOG table)
result := FALSE;
ELSE
result := TRUE;
END IF;
END;
$BODY$;
This is actually what I want; only commit if all return TRUE;
The problem is that inside the STORED_PROC_1 or _2 there are error handlings that write into a Error Log table and ... if there are errors, they will return FALSE in the result and, that in turn will call a rollback and I will loose my Error Log.
Is there a way to create a sort of a memory table that I can load with the error info and write it after the ROLLBACK? Or is there a better way to achieve this?
Thanks a lot.

Answer 1

I would suggest using FUNCTIONs rather than PROCEDUREs if you can for all of this because they have transaction control built-in in a sense. If the FUNCTION fails you automatically rollback its trasaction.
That being said, instead of doing the insert directly I would make a function like the following:
CREATE OR REPLACE FUNCTION func_logerror(error TEXT, errortype TEXT, date DATE DEFAULT CURRENT_DATE)
RETURNS SETOF ERROR_LOG
AS $$
DECLARE
BEGIN
RETURN QUERY
INSERT INTO ERROR_LOG VALUES (error, errortype, date) RETURNING *;
END;
$$;
Call it using either SELECT or PERFORM depending on whether or not you want the results in the calling function.
PERFORM * FROM func_logerror('Error', 'Type of Error', CURRENT_DATE);
After reading your answer response I've come up with this to help clarify. I was suggesting not using stored procedures at all. Instead handle your error cases in a different manner:
-- (MAIN STORED PROCEDURE)
CREATE OR REPLACE FUNCTION FUNC_MAIN()
RETURNS boolean
AS $$
DECLARE
res boolean;
BEGIN
SELECT * INTO res FROM FUNC_1('WW','TT','FF');
IF res = TRUE
THEN
SELECT * INTO res FROM FUNC_2('a','b','c');
...
ELSE
RETURN FALSE;
END IF;
RETURN res;
END;
$$;
-- (END MAIN STORED PROCEDURE)
-------
--Example of Stored Procedure 1
CREATE OR REPLACE FUNCTION FUNC_1 (a TEXT, b TEXT, c TEXT)
RETURNS boolean
AS $$
DECLARE
BEGIN
-- ****complete data validation before writing to tables****
-- If you hit any invalid data return out of the function before writing any persistent data
-- Ex:
IF COALESCE(a, '') = '' -- could be anything that may produce ERROR_FOUND from your example
THEN
RAISE WARNING 'FUNC_1 | param: a: must have a value';
PERFORM * FROM "Schema".func_errlog('Error','Type of Error',CURRENT_DATE);
RETURN FALSE;
END IF;
RETURN TRUE; -- If you've made it to the end of the function there should be no errors
END;
$$;