bitmap index

说明：

set echo on
drop table t purge;

create table t
( processed_flag varchar2(1)
);
create bitmap index
t_idx on t(processed_flag);
insert into t values ( ‘N‘ );
declare
    pragma autonomous_transaction;
begin
    insert into t values ( ‘N‘ );
    commit;
end;
/

如果数据在一个回话里执行会出现锁死错误，所以尽量不要用 bitmap index