> Anyway, on my machine it seems that the per-tuple CPU costs for SELECT > COUNT(*) with an index-only scan are something like 10% higher than the > per-tuple costs with a heap scan. We might get that down to roughly par > with some hacking, but it's never going to be vastly better. The > argument in favor of index-only scans is mainly about reducing I/O costs > anyway.
Well, if it's not CPU costs, then something else is eating the time, since I'm seeing per-tuple COUNT counts on indexes being 400% more than on heap. In the airport you said something about index-only scan not scanning the tuples in leaf page order. Can you elaborate on that? -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
