higepon <hige...@gmail.com> writes: > But I don't understand this case. > select * from emp where emp_no > 10000; > Is Bitmap Scan is faster than Index Scan in this case ?
Yes, very probably, if a lot of tuples are being retrieved. A bitmap scan will fetch the tuples from the heap in a more or less optimal fashion --- for instance, each page is read only once. Index scan will result in a random sequence of accesses to the heap. (Of course, it might have some order if the index is well correlated with the heap order, but most of the time that's not true.) regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers