Re: [COMMITTERS] pgsql: Make large sequential scans and VACUUMs work in a limited-size

[Alvaro Herrera <alvherre(at)commandprompt(dot)com>]

Tom Lane wrote:
> Log Message:
> -----------
> 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?

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.