From: Richard Huxton <dev@archonet.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jan Wieck <JanWieck@Yahoo.com>
Cc: 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 18:49:14 +0100
Message-ID: <4123969A.4020509@archonet.com> (raw)
In-Reply-To: <1803.1092847586@sss.pgh.pa.us>
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>
<41236277.5060903@Yahoo.com>
<22808.1092842209@sss.pgh.pa.us>
<41237DA2.9090405@archonet.com>
<1535.1092845917@sss.pgh.pa.us>
<4123837C.30408@Yahoo.com>
<1803.1092847586@sss.pgh.pa.us>
Tom Lane wrote:
> Jan Wieck <JanWieck@Yahoo.com> writes:
>
>>If we allow for a unique index, that
>> * it is NOT maintained (no index tuples in there)
>> * depends on another index that has a subset of columns
>> * if that subset-index is dropped, the index becomes maintained
>>then the uncertainty is gone. At the time someone drops the other
>>constraint or unique index, the data is unique with respect to the
>>superset of columns. So building the unique index data at that time will
>>succeed.
>
>
> My goodness this is getting ugly. The notion of having to invoke an
> index build as a side-effect of a DROP sounds like a recipe for trouble.
I'm not sure it needs to be as clever as Jan suggested (but then I'm not
as clever as Jan :-). I'd have thought a reference that forces you to
use DROP...CASCADE would be enough. In those cases where you're dropping
a whole table, presumably that's already implied.
--
Richard Huxton
Archonet Ltd
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To: pgsql-sql@postgresql.org
Cc: dev@archonet.com, tgl@sss.pgh.pa.us, 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: <4123969A.4020509@archonet.com>
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