I create a table with 43kk rows, populate them with values 1..200. So ~220k per each number spreaded through the table.

create table foo (id integer primary key, val bigint);
insert into foo ;
select i, random() * 200 from generate_series(1, 43000000) as i;
create index val_index on foo(val);
vacuum analyze foo;
explain analyze select id from foo where val = 55;

Result: at depesz

I except total runtime < 1s, is it possible? I have SSD, core i5 (1,8), 4gb RAM. 9,3 Postgres.

If I use Index Only scan it works very fast:

explain analyze select val from foo where val = 55;

at depesz But I need to select id not val so Incex Only scan is not suitable in my case. Thanks in advance!