Re: challenging constraint situation - how do I make it

Kenneth Downs wrote:
> Alban Hertroys wrote:
>
>> When encountering this problem I usually wonder why there isn't a data
>> type that can store a timestamp and can be used to create a UNIQUE
>> INDEX over it's values. That'd be wonderful.
>> Well, maybe one day I'll actually have time to create one...
>>
> I tried this at trigger level. The real bear is in the fact that there
> are two columns, not one. It is trivial to write an exclusion
> constraint that disallows overlapping (including nested) values. What
> was hard was determining the meta-data structure, how do you have two
> columns that are sometimes treated as one and sometimes as two?

Are you refering to a 'timespan' data type that can be determined to be
unique?

I can see some problems there, as both value and range matter; it'd be
similar to determining the uniqueness of an area in a rectangle (though
1 dimensional only, of course).

I've never really dug into this, so I don't know what possibilities
PostgreSQL offers in this field. Basing this on faith :)

Regards,
--
Alban Hertroys
alban(at)magproductions(dot)nl

magproductions b.v.

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