On Tue, Mar 11, 2014 at 10:06 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> But not sure how to define a unique
> index that allows (joe, db1) to coexist with (joe, db2) but not with
> (joe, 0).
>
and why you want that restriction? when you login you need to specify
the db, right? if you don't specify the db then is the global 'joe'
that want to login
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