On Mon, May 11, 2020 at 07:41:55PM -0500, Justin Pryzby wrote:
> On Mon, May 11, 2020 at 10:52:41AM +0530, Amit Kapila wrote:
> > One more observation:
> >
> > Allow inserts to trigger autovacuum activity (Laurenz Albe, Darafei
> > Praliaskouski)
> > This new behavior allows pages to be set as all-visible, which then
> > allows index-only scans, ...
>
> > The above sentence sounds to mean that this feature allows index-only
> > scans in more number of cases after this feature. Is that what you
> > intend to say? If so, is that correct? Because I think this will
> > allow index-only scans to skip "Heap Fetches" in more cases.
>
> I think what you mean is that the autovacuum feature, in addition to
> encouraging the *planner* to choose an indexonly scan, will *also* allow (at
> execution time) fewer heap fetches for a plan which would have
> already/previously used IOS. Right ? So maybe it should say "allows OR
> IMPROVES index-only scans" or "allows plans which use IOS to run more
> efficiently".
Yes, I see your point now. New text is:
This new behavior reduces the work necessary when the table
needs to be frozen and allows pages to be set as all-visible.
All-visible pages allow index-only scans to access fewer heap rows.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
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