From: Jan Wieck <JanWieck@Yahoo.com>
To: Markus Bertheau <twanger@bluetwanger.de>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: olly@lfix.co.uk, pgsql-sql@postgresql.org, Bruce Momjian <pgman@candle.pha.pa.us>
Subject: Re: multi column foreign key for implicitly unique columns
Date: Wed, 18 Aug 2004 10:06:47 -0400
Message-ID: <41236277.5060903@Yahoo.com> (raw)
In-Reply-To: <1092836961.2630.3.camel@dicaprio.akademie1.de>
References: <1092734724.2627.4.camel@dicaprio.akademie1.de>
<1092735576.28365.48.camel@linda>
<1092736197.2627.12.camel@dicaprio.akademie1.de>
<200408171945.15663.josh@agliodbs.com>
<41235A90.1080300@Yahoo.com>
<1092836961.2630.3.camel@dicaprio.akademie1.de>
On 8/18/2004 9:49 AM, Markus Bertheau wrote:
> В Срд, 18.08.2004, в 15:33, Jan Wieck пишет:
>
>> Meaning that not enforcing the uniqueness of those columns isn't an
>> option.
>
> The thing is that the columns _are_ unique, there's just no unique
> constraint on them. They are unique because there's a unique constraint
> on a subset of these columns. So no additional uniqueness enforcing
> needed.
>
Yes, you are right, a superset of columns of a unique constraint is
allways unique as well.
I assume it is performance why you are denormalizing your data?
However, Bruce, this should be on the TODO list:
* Allow foreign key to reference a superset of the columns
covered by a unique constraint on the referenced table.
Jan
--
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Cc: JanWieck@Yahoo.com, twanger@bluetwanger.de, josh@agliodbs.com, pgman@candle.pha.pa.us
Subject: Re: multi column foreign key for implicitly unique columns
In-Reply-To: <41236277.5060903@Yahoo.com>
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