plpgsql functing does not use index....

Hi Postgres people!

yes, I googled a lot for an answer to this question and found out that
it was asked
several times, but I could not find a sufficient answer. So here goes
my problem:

I am evaluating PostgreSQL at the moment. I got a table with about
4,500,000 rows - something I allways use for testing.

This is my table:

    public    adressen    id        -5    int8    8
    public    adressen    name    12    varchar    255
    public    adressen    strasse    12    varchar    255
    public    adressen    ort        12    varchar    255
    public    adressen    telefon    12    varchar    255

It has an index on name:
public    adressen_ixname    name    12    varchar    255

I use a plpgsql function to select data from the table.
Here is my function:

create or replace function fnc_selAdressByName(varchar, integer,
integer) returns setof adressen as '
declare

     rec public.adressen%ROWTYPE;

     pName alias for $1;
     pLimit alias for $2;
     pOffset alias for $3;

begin

     for rec in select * from public.adressen
                where name like pName
                order by name
                limit pLimit offset pOffset
     loop
         return next rec;
     end loop;

     return;
end

' language 'plpgsql';

I call the function with: select * from
fnc_selAdressByName('Hasemann%', 5, 0);
The request takes about 22 sec.

When I execute the query of the function directly:
select * from public.adressen where name like 'Hasemann%'  order by
name  limit 5 offset 0
the request takes about 0.058 sec.

So I get the idea that the query uesn in the plpgsql function did not
use the adressen_ixname index.

Why????? What can I do to make it use the index?????

Thx for any help!!!

Regards,
Ralf Hasemann