Triggers/perform oddity between 7.2 and 7.3

Hi gurus,

Anyone knows how to solve this? I was playing around with triggers on
my own machine which runs 7.3 and there it works okey, but when trying
it on 7.2 I get an error about duplicate keys. Upgrading to 7.3 on the
other machines is not possible yet. Any help on getting it to work
with 7.2 would be appreciated.


create table a(
        n       varchar,
        x       int,
        y       int,
        z       int
);

create table b(
        n       varchar,
        x_sum   int,
        y_sum   int,
        z_sum   int,

        primary key(n)
);

create function plpgsql_call_handler() returns language_handler as
'/usr/lib/postgresql/lib/plpgsql' language c;
create language plpgsql handler plpgsql_call_handler;

create function "a_trigger"() returns "trigger" as '
declare n_rows integer;
begin
        if (tg_op = ''INSERT'') then
                perform n from b where n = new.n; -- Problem is here
                if not found then                 -- I think..
                        insert into b (
                                n,
                                x_sum,
                                y_sum,
                                z_sum
                        ) values (
                                new.n,
                                new.x,
                                new.y,
                                new.z
                        );
                else
                        update b set
                                x_sum = x_sum + new.x,
                                y_sum = y_sum + new.y,
                                z_sum = z_sum + new.z
                        where n = new.n;
                end if;
                return new;
        end if;
        if (tg_op = ''DELETE'') then
                perform n from a where n = old.n;
                get diagnostics n_rows = ROW_COUNT;
                if n_rows = 1 then
                        delete from b where n = old.n;
                else
                        update b set
                                x_sum = x_sum - old.x,
                                y_sum = y_sum - old.y,
                                z_sum = z_sum - old.z
                        where n = old.n;
                end if;
                return old;
        end if;
        if (tg_op = ''UPDATE'') then
                update b set
                        x_sum = x_sum - old.x + new.x,
                        y_sum = y_sum - old.y + new.y,
                        z_sum = z_sum - old.z + new.z
                where n = new.n;
                return new;
        end if;
end
' language 'plpgsql';

create trigger a_trigger before insert or update or delete on a for
each row execute procedure a_trigger();


In 7.2.1 I get error:

trigger_test=# insert into a values('a', 1, 2, 3);
INSERT 49555 1
trigger_test=# insert into a values('a', 1, 2, 3);
NOTICE:  Error occurred while executing PL/pgSQL function a_trigger
NOTICE:  line 6 at SQL statement
ERROR:  Cannot insert a duplicate key into unique index b_pkey
trigger_test=# select version();
                            version
---------------------------------------------------------------
 PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.95.4
(1 row)

In 7.3.3 it works fine:

trigger_test=# insert into a values('a', 1, 2, 3);
INSERT 456365 1
trigger_test=# insert into a values('a', 1, 2, 3);
INSERT 456366 1
trigger_test=# select version();
                                    version
-------------------------------------------------------------------------------
 PostgreSQL 7.3.3 on i386-pc-linux-gnu, compiled by GCC gcc (GCC) 3.3
(Debian)
(1 row)

Thanks.

--
Riddler & Headcrusher - Plasma Fire