Horton

Re: Covering Indexes

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, Jeff Janes <jeff.janes@gmail.com>, "David E. Wheeler" <david@justatheory.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2012-06-28T16:32:43Z
Lists: pgsql-hackers 
Alvaro Herrera <alvherre@commandprompt.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