Re: Patch: Write Amplification Reduction Method (WARM)

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, 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: 2017-03-21 13:30:29
Message-ID: 20170321133029.dfjxrso7g6fgjrhe@alvherre.pgsql
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Amit Kapila wrote:

> I think it is because heap_getattr() is not that cheap. We have
> noticed the similar problem during development of scan key push down
> work [1].

One possibility to reduce the cost of that is to use whole tuple deform
instead of repeated individual heap_getattr() calls. Since we don't
actually need *all* attrs, we can create a version of heap_deform_tuple
that takes an attribute number as argument and decodes up to that point.

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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