Question about no unchanging update rule + ALTER

[Josh Trutwin <josh@xxxxxxxxxxxxxxxxxxx>]

I found the following on a blog post
(http://www.depesz.com/index.php/2007/09/08/avoiding-empty-updates/)
which had a rule to prevent empty updates:

CREATE RULE no_unchanging_updates AS
ON UPDATE
TO test_table
WHERE ROW(OLD.*) IS NOT DISTINCT FROM ROW(NEW.*)
DO INSTEAD NOTHING;

Works great, but problem comes when I alter the table and add a new
column, it appears the rule doesn't allow an update after adding a
new column via ALTER TABLE ADD COLUMN.

I created the rule above, then did:

ALTER TABLE test_table ADD COLUMN foo TEXT;

=> UPDATE test_table SET foo = 'bar';
UPDATE 0

When doing a \d on the table I notice the rule is expanded at the
time of creation to include each column in an expression, but it is
not updated from the ALTER TABLE command.

Do I have to drop and recreate this rule after every ALTER TABLE
ADD/DELETE column?  Or would the following trigger (also found on
blog post) be a better solution as my app is for a "plugin" builder
where adding/deleting/changing fields is common:

CREATE OR REPLACE FUNCTION prevent_empty_updates() RETURNS trigger as
$BODY$
DECLARE
  BEGIN
    IF ROW(OLD.*) IS DISTINCT FROM ROW(NEW.*) THEN
      RETURN NEW;
    END IF;
    RETURN NULL;
  END;
$BODY$ language plpgsql;

CREATE TRIGGER prevent_empty_updates BEFORE UPDATE ON test FOR EACH
ROW EXECUTE PROCEDURE prevent_empty_updates();

Actually after writing this, this TOO does not seem to work after an
ADD COLUMN.  :/  Any suggestions?

Postgres version is 8.3.

Thanks,

Josh

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