CURRENT_DATE in postgresql triggers - sql

Question

I have before insert trigger in postgres
CREATE OR REPLACE FUNCTION add_requestdate() RETURNS TRIGGER AS $$
DECLARE
BEGIN
new.requestdate := now();
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER addrequestdate
BEFORE INSERT ON requests FOR EACH ROW EXECUTE PROCEDURE add_requestdate ();
But it doesn't work! I have solution that works...
CREATE OR REPLACE FUNCTION add_requestdate() RETURNS TRIGGER AS $$
DECLARE
BEGIN
UPDATE requests SET requestdate=now() WHERE id=NEW.id;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER addrequestdate
BEFORE INSERT ON requests FOR EACH ROW EXECUTE PROCEDURE add_requestdate ();
I have only one question. Why new.requestdate := now(); doesn't work?

Answer 1

it working - probably you have some other dependency - it strange, your workable solution cannot to work, because before trigger doesn't see a tuple in table, and if you use after trigger, then you start recursion..
postgres=# create table x(a int, b date, c timestamp);
CREATE TABLE
postgres=# create function fxx()
postgres-# returns trigger as $$
postgres$# begin
postgres$# new.b := now();
postgres$# new.c := now();
postgres$# return new;
postgres$# end;
postgres$# $$ language plpgsql;
CREATE FUNCTION
postgres=# create trigger xxxx before insert on x for each row execute procedure fxx();
CREATE TRIGGER
postgres=# insert into x(a) values(10);
INSERT 0 1
postgres=# insert into x(a) values(209);
INSERT 0 1
postgres=# select * from x;
a │ b │ c
─────┼────────────┼────────────────────────────
10 │ 2012-01-07 │ 2012-01-07 18:36:57.665283
209 │ 2012-01-07 │ 2012-01-07 18:37:00.853442
(2 rows)
so, you can use CURRENT_DATE instead now(), it is preferable solution.