I wrote this simple piece of code in vertica 7.1.2
select reenable_duplicate_key_error();
create table Person(id int PRIMARY KEY, firstname varchar(20));
insert into Person select 1, 'test1' union all select 1, 'test2' union all select 1, 'test3';
Now if I do a
select * from Person;
i see
id | firstname
----+-----------
1 | test1
1 | test2
1 | test3
(3 rows)
so it seems there is no effect of marking a key as primary key