Re: Patch: Write Amplification Reduction Method (WARM)

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch: Write Amplification Reduction Method (WARM)
Date: 2017-02-23 18:26:09
Message-ID: 20170223182609.ymowqb7pj3m4vlbx@alvherre.pgsql
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Bruce Momjian wrote:
> On Thu, Feb 23, 2017 at 03:03:39PM -0300, Alvaro Herrera wrote:
> > Bruce Momjian wrote:
> >
> > > As I remember, WARM only allows
> > > a single index-column change in the chain. Why are you seeing such a
> > > large performance improvement? I would have thought it would be that
> > > high if we allowed an unlimited number of index changes in the chain.
> >
> > The second update in a chain creates another non-warm-updated tuple, so
> > the third update can be a warm update again, and so on.
>
> Right, before this patch they would be two independent HOT chains.

No, they would be a regular update chain, not HOT updates.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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