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View updating and nextval() workaround - will this ever break?

From: Richard Huxton <dev(at)archonet(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: View updating and nextval() workaround - will this ever break?
Date: 2006-10-31 09:17:44
Message-ID: 454714B8.4030605@archonet.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Basically, I'm wondering if anyone can see a problem with my standard 
workaround to the macro-expansion-vs-nextval problem with view. I can't 
see how PG changes might break it, but I might be using it in a 
presentation to others so thought I'd best check.


BEGIN;

CREATE TABLE foo (f_id serial, f1 int4, PRIMARY KEY (f_id));
CREATE TABLE bar (f_id int4 NOT NULL REFERENCES foo, b1 int4, PRIMARY 
KEY (f_id,b1));


-- This one suffers from the macro-expanding-nextval problem
--
CREATE VIEW foobar_bad AS SELECT f_id, f1, b1 FROM foo NATURAL JOIN bar;
CREATE RULE foobar_bad_ins AS ON INSERT TO foobar_bad
DO INSTEAD (
	INSERT INTO foo (f_id, f1) VALUES (nextval('foo_f_id_seq'), NEW.f1);
	INSERT INTO bar (f_id, b1) VALUES (currval('foo_f_id_seq'), NEW.b1);
);


-- This one doesn't
--
CREATE VIEW foobar_good AS SELECT f_id, f1, b1 FROM foo NATURAL JOIN bar;

CREATE FUNCTION foobar_ins_fn(p_f1 int4, p_b1 int4) RETURNS void AS $$
BEGIN
   INSERT INTO foo (f_id, f1) VALUES (nextval('foo_f_id_seq'), p_f1);
   INSERT INTO bar (f_id, b1) VALUES (currval('foo_f_id_seq'), p_b1);	
END;
$$ LANGUAGE plpgsql;

CREATE RULE foobar_good_ins AS ON INSERT TO foobar_good
DO INSTEAD SELECT foobar_ins_fn(NEW.f1, NEW.b1);


-- Bad version...
INSERT INTO foobar_bad (f1,b1)
   SELECT generate_series, generate_series+10 FROM generate_series(1,3);
SELECT * FROM foobar_bad;
DELETE FROM bar;
DELETE FROM foo;

-- Good version...
INSERT INTO foobar_good (f1,b1)
   SELECT generate_series, generate_series+10 FROM generate_series(1,3);
SELECT * FROM foobar_bad;
DELETE FROM bar;
DELETE FROM foo;

COMMIT;

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