Euler Taveira de Oliveira wrote:
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?).
Okay-dokay. I committed this with the constant as a #define, at value 32.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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