Simon Riggs escreveu: > On Tue, 2009-01-20 at 21:51 +0200, Heikki Linnakangas wrote: > >> Attached is a simple patch to only start skipping pages after 20 >> consecutive pages marked as visible in the visibility map. This doesn't >> do any "look-ahead", so it will always scan the first 20 pages of a >> table before it starts to skip pages, and whenever there's even one page >> that needs vacuuming, the next 19 pages will also be vacuumed. >> >> We could adjust that figure 20 according to table size. Or by >> seq_page_cost/random_page_cost. But I'm leaning towards a simple >> hard-coded value for now. > > Yes, sounds good. Can we stick to multiples of 2 as the OS readahead > does IIRC? So either 16 or 32. I'd go 32. > Agreed. And do it a constant (ALL_VISIBLE_VM_THRESHOLD?).
-- Euler Taveira de Oliveira http://www.timbira.com/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
