Ok, ich habe es geschafft, einen Testfall zu erstellen. Das Ergebnis ist, dass der Aktualisierungsteil immer ausgeführt wird, selbst bei einer frischen Einfügung. COPY scheint das Regelsystem zu umgehen. [Der Klarheit halber habe ich dies in eine separate Antwort eingefügt]
DROP TABLE pages CASCADE;
CREATE TABLE pages
( url VARCHAR NOT NULL PRIMARY KEY
, html VARCHAR
, last TIMESTAMP
);
INSERT INTO pages(url,html,last) VALUES ('www.example.com://page1' , 'meuk1' , '2001-09-18 23:30:00'::timestamp );
CREATE RULE Pages_Upsert AS ON INSERT TO pages
WHERE EXISTS (SELECT 1 from pages P where NEW.url = P.url)
DO INSTEAD (
UPDATE pages SET html=new.html , last = NOW() WHERE url = NEW.url
);
INSERT INTO pages(url,html,last) VALUES ('www.example.com://page2' , 'meuk2' , '2002-09-18 23:30:00':: timestamp );
INSERT INTO pages(url,html,last) VALUES ('www.example.com://page3' , 'meuk3' , '2003-09-18 23:30:00':: timestamp );
INSERT INTO pages(url,html,last) SELECT pp.url || '/added'::text, pp.html || '.html'::text , pp.last + interval '20 years' FROM pages pp;
COPY pages(url,html,last) FROM STDIN;
www.example.com://pageX stdin 2000-09-18 23:30:00
\.
SELECT * FROM pages;
Das Ergebnis:
url | html | last
-------------------------------+------------+----------------------------
www.example.com://page1 | meuk1 | 2001-09-18 23:30:00
www.example.com://page2 | meuk2 | 2011-09-18 23:48:30.775373
www.example.com://page3 | meuk3 | 2011-09-18 23:48:30.783758
www.example.com://page1/added | meuk1.html | 2011-09-18 23:48:30.792097
www.example.com://page2/added | meuk2.html | 2011-09-18 23:48:30.792097
www.example.com://page3/added | meuk3.html | 2011-09-18 23:48:30.792097
www.example.com://pageX | stdin | 2000-09-18 23:30:00
(7 rows)
UPDATE:Nur um zu beweisen, dass es möglich ist:
INSERT INTO pages(url,html,last) VALUES ('www.example.com://page1' , 'meuk1' , '2001-09-18 23:30:00'::timestamp );
CREATE VIEW vpages AS (SELECT * from pages);
CREATE RULE Pages_Upsert AS ON INSERT TO vpages
DO INSTEAD (
UPDATE pages p0
SET html=NEW.html , last = NOW() WHERE p0.url = NEW.url
;
INSERT INTO pages (url,html,last)
SELECT NEW.url, NEW.html, NEW.last
WHERE NOT EXISTS ( SELECT * FROM pages p1 WHERE p1.url = NEW.url)
);
CREATE RULE Pages_Indate AS ON UPDATE TO vpages
DO INSTEAD (
INSERT INTO pages (url,html,last)
SELECT NEW.url, NEW.html, NEW.last
WHERE NOT EXISTS ( SELECT * FROM pages p1 WHERE p1.url = OLD.url)
;
UPDATE pages p0
SET html=NEW.html , last = NEW.last WHERE p0.url = NEW.url
;
);
INSERT INTO vpages(url,html,last) VALUES ('www.example.com://page2' , 'meuk2' , '2002-09-18 23:30:00':: timestamp );
INSERT INTO vpages(url,html,last) VALUES ('www.example.com://page3' , 'meuk3' , '2003-09-18 23:30:00':: timestamp );
INSERT INTO vpages(url,html,last) SELECT pp.url || '/added'::text, pp.html || '.html'::text , pp.last + interval '20 years' FROM vpages pp;
UPDATE vpages SET last = last + interval '-10 years' WHERE url = 'www.example.com://page1' ;
-- Copy does NOT work on views
-- COPY vpages(url,html,last) FROM STDIN;
-- www.example.com://pageX stdin 2000-09-18 23:30:00
-- \.
SELECT * FROM vpages;
Ergebnis:
INSERT 0 1
INSERT 0 1
INSERT 0 3
UPDATE 1
url | html | last
-------------------------------+------------+---------------------
www.example.com://page2 | meuk2 | 2002-09-18 23:30:00
www.example.com://page3 | meuk3 | 2003-09-18 23:30:00
www.example.com://page1/added | meuk1.html | 2021-09-18 23:30:00
www.example.com://page2/added | meuk2.html | 2022-09-18 23:30:00
www.example.com://page3/added | meuk3.html | 2023-09-18 23:30:00
www.example.com://page1 | meuk1 | 1991-09-18 23:30:00
(6 rows)
Die Ansicht ist notwendig, um zu verhindern, dass das Rewrite-System in Rekursion geht. Die Konstruktion einer DELETE-Regel bleibt dem Leser als Übung überlassen.
