abnormal size of the on-disk file.

Hi There, <p>I have a small table  companies (< 300 rows)  and its on-disk size shows <br />abnormal <br />  <p>i
checkit as follows: <p><tt><font size="-1"> SELECT relname,relfilenode  from pg_class where
relfilenode=30977;</font></tt><br/><tt><font size="-1">  relname  | relfilenode</font></tt><br /><tt><font
size="-1">-----------+-------------</font></tt><br/><tt><font size="-1"> companies |       30977</font></tt><br
/><tt><fontsize="-1">(1 row)</font></tt><p><tt><font size="-1">ls -lsh  30977</font></tt><br /><tt><font size="-1">487M
-rw-------   1 postgres postgres     <b><font color="#CC0000">486M</font></b> Apr 26 20:27 30977</font></tt><br
/><tt><fontsize="-1">bash-2.03$</font></tt><br />  <p>i created a new table with the same content <p><tt><font
size="-1">tradein_clients=>CREATE  TABLE t_a as select * from companies;</font></tt><tt><font
size="-1"></font></tt><p><tt><fontsize="-1">SELECT</font></tt><p>its on disk file is very small <p><tt><font
size="-1">tradein_clients=>SELECT relname,relfilenode  from pg_class where relname='t_a';</font></tt><br /><tt><font
size="-1"> relname| relfilenode</font></tt><br /><tt><font size="-1">---------+-------------</font></tt><br /><tt><font
size="-1"> t_a    |    87812505</font></tt><br /><tt><font size="-1">(1 row)</font></tt><p><tt><font
size="-1">bash-2.03$ls -lsh  87812505</font></tt><br /><tt><font size="-1">196k -rw-------    1 postgres postgres    
<b><fontcolor="#000099">192k</font></b> Apr 26 20:27 87812505</font></tt><br /><tt><font
size="-1">bash-2.03$</font></tt><tt><fontsize="-1"></font></tt><p>Can anyone explain this .. <p>does unvaccuming makes
tables x2000  times largers?? <p>regds <br />mallah.