Обсуждение: rule for update view that updates/inserts into 2 tables

I’ve posted this on pgsql-general and pgsql-sql, and haven’t got any responses.  If any of you would be able to take a look at this for me and give some feedback, I’d be obliged…

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