Question

One of our Postgres tables, called rep_event, has a timestamp column that indicates when each row was inserted. But all of the rows have a timestamp value of 2000-01-01 00:00:00, so something isn’t set up right.

There is a function that inserts rows into the table, and it is the only code that inserts rows into that table – no other code inserts into that table. (There also isn’t any code that updates the rows in that table.) Here is the definition of the function:

CREATE FUNCTION handle_event() RETURNS "trigger"
AS $$
BEGIN
    IF (TG_OP = 'DELETE') THEN
        INSERT INTO rep_event SELECT 'D', TG_RELNAME, OLD.object_id, now();
        RETURN OLD;
    ELSIF (TG_OP = 'UPDATE') THEN
        INSERT INTO rep_event SELECT 'U', TG_RELNAME, NEW.object_id, now();
        RETURN NEW;
    ELSIF (TG_OP = 'INSERT') THEN
        INSERT INTO rep_event SELECT 'I', TG_RELNAME, NEW.object_id, now();
        RETURN NEW;
    END IF;
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

Here is the table definition:

CREATE TABLE rep_event
(
operation character(1) NOT NULL,
table_name text NOT NULL,
object_id bigint NOT NULL,
time_stamp timestamp without time zone NOT NULL
)

As you can see, the now() function is called to get the current time. Doing a “select now()” on the database returns the correct time, so is there an issue with calling now() from within a function?

Answer 1

A simpler solution is to just modify your table definition to have NOW() be the default value:

CREATE TABLE rep_event (
    operation character(1) NOT NULL,
    table_name text NOT NULL,
    object_id bigint NOT NULL,
    time_stamp timestamp without time zone NOT NULL DEFAULT NOW()
);

Then you can get rid of the now() calls in your trigger.

Also as a side note, I strongly suggest including the column ordering in your function… IOW;

INSERT INTO rep_event (operation,table_name,object_id,time_stamp) SELECT ...

This way if you ever add a new column or make other table changes that change the internal ordering of the tables, your function won’t suddenly break.