create table people(c1 varchar2(10));
insert into people (select 'american' from dual connect by level < 1000000);
insert into people values('russian');
create index pi on people(c1);
exec dbms_Stats.gather_table_stats(user,'people',estimate_percent=>100,method_opt=>'for all indexed columns size skewonly')
var v1 varchar2(10)
exec :v1:='russian'
select count(*) from people where c1=:v1;
exec :v1:='american'
select count(*) from people where c1=:v1;