Re: Deferred partial/expression unique constraints

On Mon, Jul 25, 2011 at 2:29 PM, Jeff Davis <pgsql@j-davis.com> wrote:
> On Fri, 2011-07-22 at 23:35 +0300, Peter Eisentraut wrote:
>> On ons, 2011-07-13 at 11:26 -0400, Tom Lane wrote:
>> > Our standard reason for not implementing UNIQUE constraints on
>> > expressions has been that then you would have a thing that claims to be
>> > a UNIQUE constraint but isn't representable in the information_schema
>> > views that are supposed to show UNIQUE constraints.  We avoid this
>> > objection in the current design by shoving all that functionality into
>> > EXCLUDE constraints, which are clearly outside the scope of the spec.
>>
>> I have never heard that reason before, and I think it's a pretty poor
>> one.  There are a lot of other things that are not representable in the
>> information schema.

+1.

> I think what Tom is saying is that the information_schema might appear
> inconsistent to someone following the spec.
>
> Can you give another example where we do something like that?

http://archives.postgresql.org/pgsql-bugs/2010-08/msg00374.php

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Robert Haas
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