Re: How to ensure that a stored function always returns TRUE or FALSE?

Thank you all for the valuable replies.

I've also got suggestions to use IS NOT DISTINCT FROM or STRICT at http://stackoverflow.com/questions/35742865/how-to-ensure-that-a-stored-function-always-returns-true-or-false 

but the former has the edge case of NULL=NULL returning TRUE

and with the latter I would have to be careful with the way I call my function -

and I am worried I might forget it later and this is a security related...

So I will probably use this function:

CREATE OR REPLACE FUNCTION check_user(in_social integer, 

        in_sid varchar(255), 

        in_auth varchar(32))

        RETURNS boolean AS

$func$

        SELECT CASE 

                WHEN in_social IS NULL THEN FALSE

                WHEN in_sid    IS NULL THEN FALSE

                WHEN in_auth   IS NULL THEN FALSE

                ELSE (MD5('secret word' || in_social || in_sid) = in_auth)

        END;

$func$ LANGUAGE sql IMMUTABLE;

Regards

Alex