Bug?

Hai,

I have encountered a problem with PostgreSQL.I have created a table
'tab1' with a column 'a' with serial type.I entered 20 records into the
table.So the query
select max(a) from tab1;
returned 20.When I tried the same query after the command
truncate table tab1;
I found that the output of the first query as

max
-----

(1 row)
When I tried to insert a new row into the table tab1 I found that the
value at column a incremented to the value 21.
But I heard from my friends that the value of the serial column gets
decremented whenever we issue the 'truncate table' command (in MS SQL
SERVER).Is the concept same with PostgreSQL or not?Can anyone clarify me on
this?

Thanks in advance,
Regards,
m.Indira