From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Freezing without write I/O |
Date: | 2013-06-01 22:56:30 |
Message-ID: | CA+U5nMJvDNZzBxFEP9gSk_TuGD2+kL0d9JgA2S5yn4ODDv2uhA@mail.gmail.com |
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On 1 June 2013 21:26, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sat, Jun 1, 2013 at 3:22 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> If we set a bit, surely we need to write the page. Isn't that what we
>> were trying to avoid?
>
> No, the bit only gets set in situations when we were going to dirty
> the page for some other reason anyway. Specifically, if a page
> modification discovers that we've switched epochs (but just once) and
> the bit isn't already set, we can set it in lieu of scanning the
> entire page for tuples that need freezing.
>
> Under this proposal, pages that don't contain any dead tuples needn't
> be dirtied for freezing, ever. Smells like awesome.
Agreed, well done both.
What I especially like about it is how little logic it will require,
and no page format changes.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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