Brandon Craig Rhodes [EMAIL PROTECTED] writes:
The current CVS version of PostgreSQL gives us the error:
ERROR: UNION/INTERSECT/EXCEPT member statement
may not refer to other relations of same query level
when given the following test case, despite the fact that the EXCEPT
clause does not refer to any other relation involved in the same
query.
CREATE OR REPLACE RULE current_delete AS
ON DELETE TO current
DO INSERT INTO former (number)
SELECT number FROM current
WHERE number = OLD.number
EXCEPT
SELECT number FROM trash;
But in fact OLD is a relation reference. You have to remember that when
you issue, say,
DELETE FROM current WHERE date '2002-02-01'
(I'm just making up an example of a WHERE-condition here), the rule
action gets rewritten to something like
INSERT INTO former (number)
SELECT current.number FROM current, current OLD
WHERE current.number = OLD.number
AND OLD.date '2002-02-01'
I've left off the EXCEPT part in my example of the rewritten query,
because I'm not sure where the OLD reference could get put if the
rule action involves an EXCEPT. The code doesn't know either :-(
You may find that the most practical way to handle this requirement
is to put the insertion-into-former command into a trigger procedure
rather than a rule.
regards, tom lane
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