| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Gokulakannan Somasundaram <gokul007(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: An idle thought |
| Date: | 2010-03-18 21:48:39 |
| Message-ID: | 1268948919.4053.535.camel@monkey-cat.sm.truviso.com |
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| Lists: | pgsql-hackers |
On Thu, 2010-03-18 at 17:17 -0400, Tom Lane wrote:
> > The VM cause wrong results if a bit is set that's not supposed to be --
> > right? Am I missing something? How does a seq scan skip visibility
> > checks and still produce right results, if it doesn't rely on the bit?
>
> It doesn't. The only thing we currently rely on the VM for is deciding
> whether a page needs vacuuming
Oh, my mistake. I misremembered the discussion and I thought the seq
scan optimization made it in.
> In order to do things like not visiting a page during scans, we'll have
> to solve the reliability issues.
Yeah, and also for the index-only scans.
Regards,
Jeff Davis
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