Re: Skip all-visible pages during second HeapScan of CIC

From: David Steele <david(at)pgmasters(dot)net>
To: Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Skip all-visible pages during second HeapScan of CIC
Date: 2017-03-21 18:33:33
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On 3/7/17 9:42 PM, Pavan Deolasee wrote:
> Fair point. I'm not going to "persist" with the idea too long. It seemed
> like a good, low-risk feature to me which can benefit certain use cases
> quite reasonably. It's not uncommon to create indexes (or reindex
> existing indexes to remove index bloats) on extremely large tables and
> avoiding a second heap scan can hugely benefit such cases. Holding up
> the patch for something for which we don't even have a proposal yet
> seemed a bit strange at first, but I see the point.
> Anyways, for a recently vacuumed table of twice the size of RAM and on a
> machine with SSDs, the patched CIC version runs about 25% faster. That's
> probably the best case scenario.
> I also realised that I'd attached a slightly older version of the patch.
> So new version attached, but I'll remove the patch from CF if I don't
> see any more votes in favour of the patch.

I have marked this submission "Returned with Feedback". Please feel
free to resubmit to a future commitfest or open a discussion on hackers
if you develop a new approach.


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