BUG #6551: PL/pgSQL: GET DIAGNOSTICS not working for first OUT parameter

The following bug has been logged on the website:

Bug reference: 6551
Logged by: Adam Buraczewski
Email address: aburacze(at)gmail(dot)com
PostgreSQL version: 9.1.3
Operating system: Linux (Fedora 16)
Description:

Hi!

I have just found strange behaviour of PL/pgSQL in case of using OUT
parameters and GET DIAGNOSTICS var = ROW_COUNT (PostgreSQL 9.1.3). Here is a
self-contained example:

create table t (c integer);

create function p(out x1 integer, out x2 integer, out x3 integer)
as $$
begin
insert into t values (1);
get diagnostics x1 = row_count;
insert into t values (2);
get diagnostics x2 = row_count;
insert into t values (3);
get diagnostics x3 = row_count;
end;
$$ language plpgsql;

select * from p();

x1 | x2 | x3
----+----+----
| 1 | 1

Why x1 is NULL instead of the value 1? I found a workaround: declare a
temporary variable inside the function then assign ROW_COUNT to that
variable and then assign temporary variable to the OUT parameter. It works
but probably is not the solution one could expect:

create function p_workaround(out x1 integer, out x2 integer, out x3
integer)
as $$
declare
tmpvar integer;
begin
insert into t values (1);
get diagnostics tmpvar = row_count;
x1 := tmpvar;
insert into t values (2);
get diagnostics x2 = row_count;
insert into t values (3);
get diagnostics x3 = row_count;
end;
$$ language plpgsql;

select * from p_workaround();

x1 | x2 | x3
----+----+----
1 | 1 | 1

Best regards,
Adam