Re: Covering Indexes

On Thu, Jun 28, 2012 at 9:12 AM, Alvaro Herrera
<alvherre@commandprompt.com> wrote:
>
> Excerpts from Tom Lane's message of jue jun 28 12:07:58 -0400 2012:
>
>> When this came up a couple weeks ago, the argument that was made for it
>> was that you could attach non-significant columns to an index that *is*
>> unique.  That might or might not be a wide enough use-case to justify
>> adding such a horrid kludge.
>
> The other question is whether such an index would prevent an update from
> being HOT when the non-indexed values are touched.

That seems like an easy question to answer.  How could it not disable
HOT and still work correctly?

> That could be a
> significant difference.

True, adding the covering column would not always be a win.  But
surely it more likely to be a win when it can be done without adding
yet another index that also needs to be maintained.

Cheers,

Jeff