Subject: Re: [PROPOSAL] Covering + unique indexes.
To: Anastasia Lubennikova <a.lubennikova@postgrespro.ru>,
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From: Vik Fearing <vik@2ndquadrant.fr>
Message-ID: <55F7FFFF.6010904@2ndquadrant.fr>
Date: Tue, 15 Sep 2015 13:24:47 +0200
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On 09/15/2015 12:45 PM, Anastasia Lubennikova wrote:
> 15.09.2015 12:11, Vik Fearing:
>> On 09/15/2015 10:57 AM, David Rowley wrote:
>>>> I agree, that form
>>>>> CREATE UNIQUE INDEX i ON t (f1, f2, f3) INCLUDE (f4)
>>>>> is clear. f4 will be used in row compare and actually planner will
>>>>> be able
>>>>> to use it as unique index (f1, f2, f3) with additional f4 or as
>>>>> as unique index (f1, f2, f3, f4), because uniqueness on (f1, f2,
>>>>> f3) gives
>>>>> warranty of uniqueness on (f1, f2, f3, f4)
>>>>>
>>>>>
>>> I'd vote for this too. However, INCLUDE does not seem to be a
>>> reserved word
>>> at the moment.
>> What about CREATE UNIQUE INDEX i ON t (f1, f2, f3) WITH (f4); ?
> 
> WITH seems ambiguity to me. It refers to CTE, so I expect to see after
> that a kind of query expression. But maybe that's just matter of habit.

Not necessarily. See WITH ORDINALITY, for example. However, now that
I've looked at it, index creation already takes a WITH clause for
storage parameters, so that's out.

> BTW, that's the first syntax change I'm working with.
> Is there any convention in PostgreSQL about new keywords and so on?
> Where can I find it?

I don't think it's written anywhere except peppered throughout the
archives. New keywords are greatly frowned upon.

INCLUDING is already an unreserved keyword, and sounds more natural than
INCLUDE anyway. Maybe that could work?
-- 
Vik Fearing                                          +33 6 46 75 15 36
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support


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