On 09/08/18 21:09, Bruce Momjian wrote:
> On Thu, Aug 9, 2018 at 01:11:05PM +0300, KES wrote:
>> Bruce:
>>> Yes, it would work, but doing that only for equality would be
>>> surprising
>> to many people
>>
>> Why surprising? It is
>> [documented](https://www.postgresql.org/docs/current/static/sql-create
>> table.html#sql-createtable-exclude):
>>> If all of the specified operators test for equality, this is
>>> equivalent to a UNIQUE constraint, although an ordinary unique
>>> constraint will be faster.
>>
>> Thus the UNIQUE constraint is just particular case of exclusion
>> constraint, is not?
>
> Well, for me a UNIQUE constraint guarantees each discrete value is
> unique, while exclusion constraint says discrete or ranges or geometric
> types don't overlap. I realize equality is a special case of discrete,
> but having such cases be marked as UNIQUE seems too confusing.
One of the things I'm currently trying to implement is the WITHOUT
OVERLAPS for UNIQUE constraints.
See SQL:2016 section 11.7 <unique constraint definition>
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http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
