BUG #1860: Insert failed due to unique index

The following bug has been logged online:

Bug reference:      1860
Logged by:          Viswanath Ramineni
Email address:      v_ramineni@hotmail.com
PostgreSQL version: 8.1 Beta
Operating system:   Windows 2000 Professional
Description:        Insert failed due to unique index
Details:

I have a table with a primary key on id (integer) column and a unique index
on varchar(10) column. Insertion fails when the value of the unique column
is substring of an existing value. For example, if I have a row with the
unique column value 'TEST1', it will not allow me insert another row with
'TEST' as the value for this column.