Hello! I have read pgsql online docs but still need helps. (And pardon me for cross posting to pgsql-novice as I have not received responses to my problem.) I want to increment the value of field SocialSecurityNo in a centrally controlled table SocialSecurityTable. SocialSecurityTable contains only one row and one field - SocialSecurityNo. Because, I think, SocialSecurityNo in SocialSecurityTable should not even be read by any other user when it is being incremented by a user (or the number will duplicate), and setting transaction isolation level seems to be not restrictive enough in this case, I use table lock as follows: CREATE FUNCTION GetAndSetNextNumber () RETURNS TEXT AS ' DECLARE UsedNumber TEXT; BEGIN BEGIN WORK; LOCK SocialSecurityTable IN ROW EXCLUSIVE MODE; SELECT SocialSecurityNo INTO UsedNumber FROM SocialSecurityTable; --Do a lot of calculation on UsedNumber -- and generate the next free SocialSecurityNo -- and assign this free value to UsedNumber. UPDATE SocialSecurityTable SET SocialSecurityNo=UsedNumber; COMMIT WORK; RETURN UsedNumber; END;' LANGUAGE 'plpgsql'; Question A: Is this above function apporpriately designed, or are there more efficient ways than table locking? Question B: I think statement "LOCK SocialSecurityTable IN ROW EXCLUSIVE MODE;" will fail when this user (user A) executed this statement AFTER another user (user B) and user B has not yet COMMITed his transaction? What are the solutions for this (LOCK TABLE fails in function)? Regards, CN
