Re: Documentation for create unique index is insuficient and (because of that) incorrect

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: "Jonathan S(dot) Katz" <jkatz(at)postgresql(dot)org>, Bruce Momjian <bruce(at)momjian(dot)us>, emilioplatzer(at)gmail(dot)com, pgsql-docs(at)lists(dot)postgresql(dot)org
Subject: Re: Documentation for create unique index is insuficient and (because of that) incorrect
Date: 2018-11-20 18:15:30
Message-ID: 26034.1542737730@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> On 2018-Nov-20, Tom Lane wrote:
>> I'm also wondering whether to move that section someplace earlier
>> in chapter 11. Right now it's near the end because it's mostly
>> info about an implementation detail; but it wouldn't be hard to
>> make the argument that covering indexes are more important than,
>> say, indexes with custom collations. Should we move it, and if
>> so to where?

> I think right next to 11.5, which currently completes the topic of how
> are indexes used, is a good place.

Well, it has to stay after 11.6 (unique indexes), because we do need
to point out that the included columns don't participate in the
uniqueness constraint, and I don't want that statement to be a forward
reference. Really this boils down to where you rank covering indexes
vs expression indexes and partial indexes in terms of usefulness.
I'd tend to put this after expression indexes, but I don't have a very
strong feeling about how to rank it versus partial indexes.

regards, tom lane

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