Re: Minimum tuple threshold to decide last pass of VACUUM

On 3 August 2015 at 17:36, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > Simon Riggs wrote:
> >> * For emergency anti-wraparound VACUUMs we shouldn't scan indexes at
> all,
> >> since they aren't critical path activities at that point
>
> > It is not possible to skip scanning indexes completely, unless no tuples
> > are to be removed from the heap.
>
> Right.
>
> > But actually this is an interesting point and I don't think we do this:
> > if in emergency mode, maybe we shouldn't try to remove any dead tuples
> > at all, and instead only freeze very old tuples.
>
> +1 ... not sure if that's what Simon had in mind exactly, but it seems
> like a correct statement of what he was getting at.
>

Yes, that's what I was thinking, I just didn't say actually it. I'd been
thinking about having VACUUM do just Phase 1 for some time, since its so
much faster to do that. Will code.

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
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