Ron Mayer <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> By definition, a bitmap scan's cost isn't affected by index order >> correlation.
> No? I think I understand that for index scans the correlation > influenced how many data pages are estimated to get sucked in. No, it's not about that, it's about whether we're likely to have to read any of those pages more than once. The bitmap processing implicitly sorts all the tuples-to-be-read into physical TID order, so the heap access is always linear no matter how badly correlated the index is. 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