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 could be a
significant difference.
--
Álvaro Herrera <alvherre@commandprompt.com>
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