trigger howto question

Furesz Peter wrote:

Hello,

I have a table named foobar and I don't want to allow from DELETE or
UPDATE
its rows.

I have a table as described below:
foobar(foobar_id, value, is_deleted);

I don't want to allow directly delete or modify the table's rows. I plan to
make an on before update or delete trigger and
on delete action I update the actual row is_deleted flag, on UPDATE
action I
also update the is_deleted flag and I insert a new row with the new values.
Everything is ok, but when I capture the delete action I am execute an
update what triggering the trigger again and I got an unwanted row.

The trick is to remember that only the trigger can be setting the
is_deleted flag, not other queries (or at least that's what I think you
want).

CREATE TRIGGER "tr_foobar" BEFORE UPDATE OR DELETE ON "public"."foobar"
FOR
EACH ROW
EXECUTE PROCEDURE "public"."tr_foobar_func"();

BEGIN
IF TG_OP='DELETE' THEN
UPDATE foobar SET is_deleted=TRUE WHERE foobar_id=OLD.foobar;
RETURN NULL;
ELSEIF TG_OP='UPDATE' THEN

^^^^^^^^^^^^^^^^^^^^^^^^^^
ELSEIF TG_OP='UPDATE' AND is_deleted=FALSE THEN

INSERT INTO foobar(value) VALUES(NEW.value);
NEW.is_deleted=TRUE;
NEW.value=OLD.value;
RETURN NEW;
END IF;
END;

Does that do what you want?

--
Richard Huxton
Archonet Ltd