full text index

Hi,

first I want to apologize, because I belive this to
be a FAQ. But I didn't find anything on www.postgresql.org
and I couldn't search the list archives (the search
never returned anything, not even "nothing found").

I have this table:

create table keywords (
kw varchar(128) not null,
hits integer not null,
primary key(kw)
)

I want to do this kind of select:

SELECT kw,hits from keywords where kw like'%xyz%';

What is the most efficient way to do it? The table
will have around 3 to 4 million rows. So a full
table scan is out of question. I need the answer in
around one second. (It's a web application)

Any ideas? Where could I read more about that?
Please advise me on finding my way around if I missed
some RTFM.

Thanks

Ulrich