Re: db_user_namespace a "temporary measure"

Andrew Dunstan <andrew@dunslane.net> writes:
> On 03/11/2014 09:37 PM, Tom Lane wrote:
>> In particular, I'd like to see an exclusion that prevents local users
>> from having the same name as any global user, so that we don't have
>> ambiguity in GRANT and similar commands.  This doesn't seem simple to
>> enforce (if we supported partial indexes on system catalogs, it would
>> be ...) but surely this representation is more amenable to enforcing it
>> than the existing one.

> Should be workable if you're creating a local name - just check against 
> the list of global roles.

Concurrent creations won't be safe without some sort of locking scheme.
A unique index would be a lot better way of plugging that hole than a
system-wide lock on user creation.  But not sure how to define a unique
index that allows (joe, db1) to coexist with (joe, db2) but not with
(joe, 0).
        regards, tom lane