[GENERAL] Creating a trigger function

[Peter Erickson]

I am running postgresql 7.4.2 and having problems creating a trigger 
function properly. I keep getting the following error:

ERROR: OLD used in query that is not in rule

I have a table called journal_entries with a foreign key to a table 
called journals. When a entry is added to journal_entries, I am trying 
to get it to update the 'mtime' field of the corresponding entry in the 
journals table.

Can anyone help me with this problem? If you need more information, 
please let me know.

CREATE OR REPLACE FUNCTION public.update_journal_mtime()
  RETURNS trigger AS
'
  DECLARE
    curtime TIMESTAMP;
  BEGIN
    curtime := \'now\';
    IF OLD IS NOT NULL THEN
      UPDATE journals SET mtime = curtime WHERE id = OLD.journ_id;
    END IF;
    IF NEW IS NOT NULL THEN
      UPDATE journals SET mtime = curtime WHERE id = NEW.journ_id;
      UPDATE journal_entries SET mtime = curtime WHERE id = NEW.id;
    END IF;
    RETURN null;
  END;
'
  LANGUAGE 'plpgsql' VOLATILE;
CREATE TRIGGER update_mtime_trigger
  AFTER INSERT OR UPDATE OR DELETE
  ON public.journal_entries
  FOR EACH ROW
  EXECUTE PROCEDURE public.update_journal_mtime();
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