tst_bool.sql

create table tst_bool (
	id bigint primary key generated always as identity,
	value numeric,
	isgood boolean
);

insert into tst_bool (value, isgood)
select random()*7, round(random()*4) = 1
from generate_series(1, 1000*1000);

analyze tst_bool;

create index idx_tst_bool on tst_bool (isgood);

explain
select id, value from tst_bool where isgood = true;

QUERY PLAN                                                                           |
-------------------------------------------------------------------------------------+
Index Scan using idx_tst_bool on tst_bool  (cost=0.42..14141.58 rows=248800 width=20)|
  Index Cond: (isgood = true)                                                        |