From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Jaime Casanova <jaime.casanova@2ndquadrant.com>
Cc: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Patch: Write Amplification Reduction Method (WARM)
Date: Thu, 23 Feb 2017 15:58:59 -0300
Message-ID: <20170223185859.fzop2i32ii5k7wk5@alvherre.pgsql> (raw)
In-Reply-To: <20170223185216.GM20486@momjian.us>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-hackers>
Bruce Momjian wrote:
> On Thu, Feb 23, 2017 at 03:45:24PM -0300, Alvaro Herrera wrote:
> > > and potentially trim the first HOT chain as those tuples become
> > > invisible.
> >
> > That can already happen even without WARM, no?
>
> Uh, the point is that with WARM those four early tuples can be removed
> via a prune, rather than requiring a VACUUM. Without WARM, the fourth
> tuple can't be removed until the index is cleared by VACUUM.
I *think* that the WARM-updated one cannot be pruned either, because
it's pointed to by at least one index (otherwise it'd have been a HOT
update). The ones prior to that can be removed either way.
I think the part you want (be able to prune the WARM updated tuple) is
part of what Pavan calls "turning the WARM chain into a HOT chain", so
not part of the initial patch. Pavan can explain this part better, and
also set me straight in case I'm wrong in the above :-)
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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Cc: alvherre@2ndquadrant.com, bruce@momjian.us, pavan.deolasee@gmail.com, jaime.casanova@2ndquadrant.com, kommi.haribabu@gmail.com, tomas.vondra@2ndquadrant.com
Subject: Re: Patch: Write Amplification Reduction Method (WARM)
In-Reply-To: <20170223185859.fzop2i32ii5k7wk5@alvherre.pgsql>
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