From: Bruce Momjian <bruce@momjian.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@2ndquadrant.com>
Cc: Jim Nasby <jim@nasby.net>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Peter Geoghegan <peter@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [PERFORM] encouraging index-only scans
Date: Tue, 11 Feb 2014 10:56:07 -0500
Message-ID: <20140211155607.GB2289@momjian.us> (raw)
In-Reply-To: <CA+TgmoYOAzNKWKdkNcq50MFQKdgSt1ESR6zxb8XKCiNO6YBX2A@mail.gmail.com>
References: <20130906170159.GB13158@momjian.us>
<20130906191330.GA13193@momjian.us>
<20130906222623.GC626072@alap2.anarazel.de>
<20130907002908.GA12753@momjian.us>
<20130907053449.GE626072@alap2.anarazel.de>
<5238854F.5040708@nasby.net>
<20130917231050.GD29545@awork2.anarazel.de>
<CA+TgmoZQyt253OA_ssD6OVs8o0-RkRz3eK6qZz3Utwp-2QVf6A@mail.gmail.com>
<20140201032207.GD31141@momjian.us>
<CA+TgmoYOAzNKWKdkNcq50MFQKdgSt1ESR6zxb8XKCiNO6YBX2A@mail.gmail.com>
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On Mon, Feb 3, 2014 at 11:55:34AM -0500, Robert Haas wrote:
> > Robert, where are we on this? Should I post a patch?
>
> I started working on this at one point but didn't finish the
> implementation, let alone the no-doubt-onerous performance testing
> that will be needed to validate whatever we come up with. It would be
> really easy to cause serious regressions with ill-considered changes
> in this area, and I don't think many people here have the bandwidth
> for a detailed study of all the different workloads that might be
> affected here right this very minute. More generally, you're sending
> all these pings three weeks after the deadline for CF4. I don't think
> that's a good time to encourage people to *start* revising old
> patches, or writing new ones.
>
> I've also had some further thoughts about the right way to drive
> vacuum scheduling. I think what we need to do is tightly couple the
I understand the problems with vacuum scheduling, but I was trying to
address _just_ the insert-only workload problem for index-only scans.
Right now, as I remember, only vacuum sets the visibility bits. If we
don't want to make vacuum trigger for insert-only workloads, can we set
pages all-visible more often?
Is there a reason that a sequential scan, which does do page pruning,
doesn't set the visibility bits too? Or does it? Can an non-index-only
index scan that finds the heap tuple all-visible and the page not
all-visible check the other items on the page to see if the page can be
marked all-visible? Does analyze set pages all-visible?
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
--
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To: pgsql-performance@postgresql.org
Cc: bruce@momjian.us, robertmhaas@gmail.com, andres@2ndquadrant.com, jim@nasby.net, alvherre@2ndquadrant.com, peter@2ndquadrant.com, tgl@sss.pgh.pa.us, andrew@dunslane.net, pgsql-hackers@postgresql.org
Subject: Re: [PERFORM] encouraging index-only scans
In-Reply-To: <20140211155607.GB2289@momjian.us>
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