Tom Lane escribió: > Gregory Stark <[EMAIL PROTECTED]> writes: > > "Manoel Henrique" <[EMAIL PROTECTED]> writes: > >> Yes, I'm relying on the assumption that backwards scan has the same cost as > >> forward scan, why shouldn't it? > > > Because hard drives only spin one direction > > Good joke, but to be serious: we expect that forward scans will result > in the kernel doing read-ahead, which will allow overlapping of > CPU work to process one page with the I/O to bring in the next page.
I wonder if this is spoiled (or rather, the backwards case fixed) by the attempts to call posix_fadvise() on certain types of scan. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
