I would like to create a rule that, by updating a view, allows me to update one table and insert into another.
The following example illustrates what I’m trying to do:
--Create Tables
CREATE TABLE my_table
(
my_table_id serial,
a character varying(255),
b character varying(255),
CONSTRAINT my_table_id_pk PRIMARY KEY (my_table_id)
);
CREATE TABLE my_audit_table
(
audit_id serial,
my_table_id int,
c character varying(255),
CONSTRAINT audit_id_pk PRIMARY KEY (audit_id)
);
--Create View
CREATE OR REPLACE VIEW my_view AS
SELECT
t.my_table_id,
t.a,
t.b,
au.audit_id,
au.c
FROM
my_table t, my_audit_table au
WHERE
t.my_table_id = au.my_table_id;
--Create Rules
CREATE OR REPLACE RULE insert_to_my_view AS
ON INSERT TO my_view
DO INSTEAD(
INSERT INTO my_table (a,b)
VALUES(new.a, new.b);
INSERT INTO my_audit_table(my_table_id, c)
VALUES
(currval('my_table_my_table_id_seq'), new.c);
);
CREATE OR REPLACE RULE update_my_view AS
ON UPDATE TO my_view DO INSTEAD
( UPDATE my_table SET
a = new.a,
b = new.b
WHERE
my_table_id = old.my_table_id;
INSERT INTO my_audit_table
(my_table_id,
c)
VALUES
(new.my_table_id,
new.c);
);
--The insert statement below inserts one row into my_table, and one row into my_audit_table
--(This works the way I would like)
insert into my_view(a,b,c) values('a contents','b contents', 'c contents');
--The update statement below doesn’t work the way I want.
--What I would like this to do is to update one row in my_table, and insert
--one row into my_audit table. It does the update fine, but the insert to my_audit_table
--doesn't work as I had anticipated.
update my_view set a = 'new a contents', b = 'new b contents', c = 'new c contents' where my_table_id = 1;
-- If I execute the above update statement multiple times, multiple rows will be
--inserted with each call after the first call.
--
--Specifically,
--after the first call, 1 row is inserted
--after the second call, 2 rows are inserted
--after the third call, 4 rows are inserted
--after the fourth call, 8 rows are inserted... and so on
--
--The problem is due to the INSERT in the update_my_view rule:
--
--INSERT INTO my_audit_table
-- (my_table_id,
-- c)
--VALUES
-- (new.my_table_id,
-- new.c);
--
--Apparently, "new.my_table_id" in this case references more than one row, if more than one row with
--the given id already exists in my_audit_table.
--
--How do I accomplish what I want to accomplish here? I'd prefer not to use a sp.
Thanks,
Chad
