From: | Greg Stark <gsstark(at)mit(dot)edu> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Martijn van Oosterhout <kleptog(at)svana(dot)org>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Unique constraints for non-btree indexes |
Date: | 2006-01-19 06:44:54 |
Message-ID: | 87hd80wwbd.fsf@stark.xeocode.com |
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Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> > I guess what you're talking about is a constrained index, of which a
> > unique index is just a particular type. I suppose the actual constraint
> > would be one of the operators defined for the operator class (since
> > whatever the test is, it needs to be indexable). Although some would
> > obviously be more useful than others...
>
> I think the generalization that would be appropriate for GIST is that
> a "unique" index guarantees there are no two entries x, y such that
> x ~ y, where ~ is some boolean operator nominated by the opclass. We'd
> probably have to insist that ~ is commutative (x ~ y iff y ~ x).
I have no big contribution here. I just want to say this is a cool idea.
These Generalized uniqueish constraints could make a lot of neat things
possible.
--
greg
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