PostgreSQL where all in array

Question

What is the easiest and fastest way to achieve a clause where all elements in an array must be matched - not only one when using IN? After all it should behave

Answer 1

create a mapping table with all possible values and use this

select 
    t1.col from conversations_users as t1 
    inner join mapping_table as map on t1.user_id=map.user_id
group by 
    t1.col  
having  
    count(distinct conversations_users.user_id)=
    (select count(distinct user_id) from mapping)