How to understand what affects the speed of query execution with an array?

Question

PostgreSQL

Good afternoon.
I have a table with 700,000 or more entries, one of the elements of which is an array of integers (int[])

create table users (uid serial primary key, username text, segments int[]); 
    insert into users (segments) values ('{0, 1, 3, 10, 5}')

etc.
Please help me understand why a type request takes much longer than a request
select * from users where segments @> '{9}' ;

select * from users where segments @> '{9, 10, 12}' ;

Answer 1

watch EXPLAIN ANALYZE VERBOSEand create an index on segments