Re: Covering Indexes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: 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 16:32:43
Message-ID: 14811.1340901163@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> The other question is whether such an index would prevent an update from
> being HOT when the non-indexed values are touched.

Surely it would *have* to, whether the columns are significant or not
for uniqueness purposes. Else an index-only scan gives the wrong value
after the update.

regards, tom lane

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