BUG #4939: error query result

The following bug has been logged online:

Bug reference: 4939
Logged by: limaozeng
Email address: limaozeng(at)163(dot)com
PostgreSQL version: 8.4.0
Operating system: linux-32 bit
Description: error query result
Details:

create table t(str char(200));
insert into t values 'mzli';
insert into t values
'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvw
xyz';
select user;
current_user
--------------
mzli
(1 row)
select * from t where str in (user,
'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk');
str

----------------------------------------------------------------------------
----------------------------------------------------------------------------
--------------------------------------------------
mzli


abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx
yz

(2 rows)

only 'mzli' ought to be appeared in the result list.