Re: Idea for getting rid of VACUUM FREEZE on cold pages

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, May 26, 2010 at 8:06 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Yeah. Neither PD_ALL_VISIBLE nor the visibility map are going to solve
>> your problem, because they cannot become set without having visited the
>> page.

> Well, maybe I'm confused here, but arranging things so that we NEVER
> have to visit the page after initially writing it seems like it's
> setting the bar almost impossibly high.

Well, that was the use-case that Josh was on about when this idea came
up: high-volume append-only log tables that in most cases will never be
read, so his client wants to get rid of the extra I/O for maintenance
visits to once-written pages.

If you're willing to allow one visit and rewrite of each page, then
we can do that today with maybe a bit of rejiggering of vacuum's
when-to-freeze heuristics.

regards, tom lane