On ons, 2011-07-13 at 11:26 -0400, Tom Lane wrote: > Dean Rasheed <dean.a.rash...@gmail.com> writes: > >>> On 7/12/11 9:46 AM, Andres Freund wrote: > >>>> 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? > > > I agree that expressing that using a UNIQUE constraint would perhaps > > be more intuitive, but it would be new non-SQL-spec syntax that AFAICS > > wouldn't actually add any new functionality. > > 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. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
