BUG #2559: why jdbc-driver AbstractJdbc2ResultSetMetaData. getTableName(int column) return ""

The following bug has been logged online:

Bug reference:      2559
Logged by:          flash.xu
Email address:      justxu@tom.com
PostgreSQL version: 8.1.4
Operating system:   fc5
Description:        why jdbc-driver AbstractJdbc2ResultSetMetaData.
getTableName(int column)  return ""
Details:

hello:
I'm using jdbc3 8.1 to build my java project.But when I use
ResultSetMetaData class to get table'name,the result is ""!
I check the jdbc8 8.1's source code,and found the
AbstractJdbc2ResultSetMetaData. getTableName(int column)  return "".
Instead, the method of "getBaseTableName()" return the real table'name.
Similar,the method of"getColumnName()"return the column'lable,but the method
of"getColumnName()" return the real column'name.
please show why?thanks.
My project has been used Oracle and Mysql.It's my first to use  PostgreSQL.

I'm come from china,and sorry for my pool English.