huh, maybe you are right, I missread that. English is not my native language.
Actually I come there from FK constraints.
Would it be sufficient for FK require not UNIQUEs, but **allow** "EXCLUDE with operators that act like equality"?
09.08.2018, 22:31, "Tom Lane" <tgl@sss.pgh.pa.us>:
> Bruce Momjian <bruce@momjian.us> writes:
>> On Thu, Aug 9, 2018 at 01:11:05PM +0300, KES wrote:
>>> 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.
>
> I think the OP is reading "equivalent" literally, as meaning that
> an EXCLUDE with operators that act like equality is treated as being
> the same as UNIQUE for *every* purpose. We're not going there, IMO,
> so probably we need to tweak the doc wording a little. Perhaps
> writing "functionally equivalent" would be better? Or instead of
> "is equivalent to", write "imposes the same restriction as"?
>
> regards, tom lane
