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Re: Covering Indexes

From: Aidan Van Dyk <aidan(at)highrise(dot)ca>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "David E(dot) Wheeler" <david(at)justatheory(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Covering Indexes
Date: 2012-06-28 16:23:52
Message-ID: CAC_2qU-GbSKjY3B2Bsrh9jY6JctPBy3pFYw-cQ+rF8TNB+J7xg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Jun 28, 2012 at 12:12 PM, Alvaro Herrera
<alvherre(at)commandprompt(dot)com> wrote:

> The other question is whether such an index would prevent an update from
> being HOT when the non-indexed values are touched.  That could be a
> significant difference.

I don't see Index-Only-Scans being something that will be used in
"high churn" tables.

So as long as the value of these "covering/included" fields is tied to
index-only scans, maybe it isn't a problem?

Of course, we have have a hard time convincing people that the  "index
only" scans they want can't be "index only" because heap pages aren't
"all visible"...

a.

-- 
Aidan Van Dyk                                             Create like a god,
aidan(at)highrise(dot)ca                                       command like a king,
http://www.highrise.ca/                                   work like a slave.

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