Outer joins don't return expected results in Oracle 10g

Question

I don't know where to report oracle bugs. So I'm writing here for someone to verify it again and report is a bug to oracle.
--Creating two table and inserting records in each tables
create table table1 ( pk_id number(6) primary key, name_tx varchar2(20) );
create table table1_nls (pk_id number(6) primary key, parent_id number(6), heading varchar2(20), lang_code varchar2(3) );
insert into table1 values( 1, 'test1' );
insert into table1_nls values( 1, 1, 'test heading', 'enu' );
--problem is with the following query.
select * from table1, (select parent_id, heading from table1_nls where lang_code = '' ) table1_nls
where table1.PK_ID = table1_nls.PARENT_ID(+) and pk_id = 1
This returns back one row in Oracle 9i, but none in oracle 10g. If I substitute " lang_code = '' " with lang_code='something' or lang_code is null it works fine. The problem is with comparing the empty value ('').
Logically lang_code is null is the right way of writing the query, but empty ('') works in Oracle 9i,
Is this a valid bug?
If not migration steps should account for this in programs.
drop table table1;
drop table table1_nls;

Answer 1

You want to go to metalink.oracle.com and create a "TAR".