Re: Deferred partial/expression unique constraints

On 12 July 2011 19:26, Josh Berkus <josh@agliodbs.com> wrote:
> On 7/12/11 9:46 AM, Andres Freund wrote:
>> Hi,
>>
>> I guess $subject wasn't implemented because plain unique indexes aren't
>> represented in pg_constraint and thus do not have a place to store information
>> about being deferred?
>> Other than that I do not see any special complications in implementing it?
>
> Um, I thought that deferrable unique constraints were a 9.0 feature, no?
>

Yes, but there is no syntax to create a unique constraint on an
expression, and hence to create a deferrable unique expression check.

However, that doesn't seem like such a serious limitation, because the
same functionality can be achieved using an exclusion constraint with
the equality operator.

Regards,
Dean