Re: timestamp (MS SQLServer's rowversion) functionality

On 10 Aug 2006 06:28:30 -0700, Andrew Hammond <
andrew(dot)george(dot)hammond(at)gmail(dot)com> wrote:
>
> Tomski wrote:
> > Hello!
> > As many of you know, SQL Server (2000) has peculiar data type
> "timestamp"
> > which is not SQL standard timestamp. In fact it is "rowversion" type. It
> > makes tha field to be updated with current timestamp when row is updated
> or
> > inserted.
> > Is there any similiar functionality in PostgreSQL? If not, how to
> achieve
> > that?
> > I need such fields in many tables. Maybe triggers could help? Do I have
> to
> > write functions for each trigger for each table? Or can it be done by
> one
> > function with parameters? Partial or final solutions are welcome :)
>
> Create your table with a column of type timestamp and DEFAULT (now())
> and you have the on insert functionality. You need to use triggers to
> get the on update fuctionality (and also for inserts if you don't trust
> the application to leave it default). I think this is actually covered
> by an example in the triggers documentation for postgres. If not then
> there's certainly a full code solution in the archives of this list.
> Please do some research before asking questions to the list.

I put a create_dt and modify_dt column on every table and set the default to
now(). Then I use this trigger:

CREATE OR REPLACE FUNCTION "public"."modify_date_stamp_fn" () RETURNS SETOF
opaque AS
'
BEGIN
-- if a trigger insert or update operation occurs
IF TG_OP = ''INSERT'' OR TG_OP = ''UPDATE'' THEN
-- assigns the current timestamp
-- into the mod_time column
NEW.modify_dt := now();

-- displays the new row on an insert/update
RETURN NEW;
END IF;
END;
'
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

CREATE TRIGGER "mytable_modify_dt_tr" BEFORE UPDATE
ON "public"."mytable" FOR EACH ROW
EXECUTE PROCEDURE "public"."modify_date_stamp_fn"();

==================================================================
Aaron Bono
Aranya Software Technologies, Inc.
http://www.aranya.com
http://codeelixir.com
==================================================================