BUG #6149: My table is empty but pg_relation_size(name) returns 39 MB

The following bug has been logged online:

Bug reference:      6149
Logged by:          Shivakumar Ramannavar
Email address:      shivasr@gmail.com
PostgreSQL version: 9.0.4
Operating system:   open SUSE Linux
Description:        My table is empty but pg_relation_size(name) returns 39
MB
Details:

Hi Team,

Though my table is empty, pg_relation_size(name) return 38 MB. I use below
query to determine tables disk usages.

SELECT nspname || '.' || relname AS "Table",
    pg_total_relation_size(C.oid) "Size",
    pg_size_pretty(pg_total_relation_size(C.oid)) AS "Total size"
  FROM pg_class C
  LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
  WHERE nspname NOT IN ('pg_catalog', 'information_schema')
    AND C.relkind <> 'i'
    AND nspname !~ '^pg_toast'

Please help,
Thanks!
Shiva