Alvaro Herrera wrote:
Tom Lane wrote:
Log Message:
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Make large sequential scans and VACUUMs work in a limited-size "ring" of
buffers, rather than blowing out the whole shared-buffer arena. Aside from
avoiding cache spoliation, this fixes the problem that VACUUM formerly tended
to cause a WAL flush for every page it modified, because we had it hacked to
use only a single buffer. Those flushes will now occur only once per
ring-ful. The exact ring size, and the threshold for seqscans to switch into
the ring usage pattern, remain under debate; but the infrastructure seems
done. The key bit of infrastructure is a new optional BufferAccessStrategy
object that can be passed to ReadBuffer operations; this replaces the former
StrategyHintVacuum API.
I think now is time to re-test the patch for advancing OldestXmin during
vacuum?
Thanks for the reminder, I'll schedule those tests.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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