No problem. I have been meaning to put the same code together for myself
but have been putting it off. It gave me an excuse to stop procrastinating.
On 7/31/06, Thusitha Kodikara <kthusi(at)yahoo(dot)com> wrote:
>
> Hello,
>
> Thanks a lot Aaron for the very quick and simple example. I just checked
> it on 7.4.5 also and it worked. I'll be able to continue with my
> development using the syntax of that example.
>
*Aaron Bono <postgresql(at)aranya(dot)com>* wrote:
>
> On 7/30/06, Thusitha Kodikara <kthusi(at)yahoo(dot)com> wrote:
> >
> > Hello,
> >
> > I am interested in developing some triggers to keep track of records
> > that are changed (possibly the changes of one or more specific columns). In
> > addition to keeping the new values, I also need to keep the old values (may
> > be on a separate table).
> >
> > Though I have done similar things in other RDBMs using SQL, I find
> > doing this in Postgres, a little bit complicated - may be because it needs
> > to be done through a separate procedural language and through a separate
> > function. The Postgres documentation also didn't provide much help ( the
> > examples in C). I was mainly looking for example showing how to refer 'OLD'
> > and 'NEW' rows using PL/pgSQL.
> >
> > Can someone please direct me to some such examples?
> >
>
>
> How about this:
>
> CREATE TABLE my_table (
> my_table_id BIGSERIAL NOT NULL,
> my_value VARCHAR(100) NOT NULL,
> CONSTRAINT my_table_pkey PRIMARY KEY (my_table_id)
> );
>
> CREATE TABLE my_table_history (
> my_table_id BIGINT NOT NULL,
> my_value VARCHAR(100) NOT NULL,
> create_dt TIMESTAMP NOT NULL,
> CONSTRAINT my_table_history_pkey PRIMARY KEY (my_table_id, create_dt)
> );
>
> CREATE OR REPLACE FUNCTION my_table_history_fn () RETURNS SETOF opaque AS
> '
> BEGIN
> -- if a trigger insert or update operation occurs
> IF TG_OP = ''INSERT'' OR TG_OP = ''UPDATE'' THEN
> execute
> ''INSERT INTO my_table_history ( '' ||
> '' my_table_id, '' ||
> '' my_value, '' ||
> '' create_dt '' ||
> '') VALUES ( '' ||
> '' '''''' || NEW.my_table_id || '''''', '' ||
> '' '''''' || NEW.my_value || '''''', '' ||
> '' now() '' ||
> '');''
> ;
> RETURN NEW;
> END IF;
> END;
> '
> LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;
>
> CREATE TRIGGER my_table_history_tr BEFORE UPDATE OR INSERT
> ON my_table FOR EACH ROW
> EXECUTE PROCEDURE my_table_history_fn();
>
> I tried it out and it works in version 8.1.
>
>
==================================================================
Aaron Bono
Aranya Software Technologies, Inc.
http://www.aranya.com
==================================================================