User logon trigger

I found the note 454088.1 on this site for create logon trigger and the log table. I do have one question though.

The create table statement as follows doesn't seem to have a primary key or unique field. Thus, cannot have indexes.

CREATE TABLE LOGONLOG(os_user varchar2(30),
user_name varchar2(30),
logon_time date,
session_user varchar2(30),
ip_address varchar2(15),
program varchar2(30));

If I were to query this table later on, will it generate lots of overhead hence jeopardize the performance of database?