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Re: [COMMITTERS] pgsql: Make large sequential scans and VACUUMs work in a limited-size
- From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
- To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
- Cc: Hackers <pgsql-hackers(at)postgresql(dot)org>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
- Subject: Re: [COMMITTERS] pgsql: Make large sequential scans and VACUUMs work in a limited-size
- Date: Thu, 31 May 2007 10:11:30 +0100
- Message-id: <465E9142.1050101@enterprisedb.com> <text/plain>
Alvaro Herrera wrote:
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?
Thanks for the reminder, I'll schedule those tests. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
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