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Re: What are the advantages of not being able to access multiple databases with one connection?

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: crocket <crockabiscuit(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: What are the advantages of not being able to access multiple databases with one connection?
Date: 2012-11-05 23:50:22
Message-ID: CAHyXU0y2fK5c0tm7itdVoe3gBbD=LuSJxkOoV9=rjVUH0XzsBw@mail.gmail.com (view raw or flat)
Thread:
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On Mon, Nov 5, 2012 at 11:33 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, Oct 30, 2012 at 8:37 AM, crocket <crockabiscuit(at)gmail(dot)com> wrote:
>> MySQL permits a connection to access multiple databases.
>> But Postgresql restricts a connection to one database.
>> I think postgresql database connection is somewhat limited.
>>
>> Is it an old and decrepit design? or does it deserve some appreciations?
>
> I think it deserves some appreciation.  Each database is completely
> isolated in terms of privileges, which is sometimes useful.  Also, if
> you somehow manage to fry the system catalogs in one database, the
> other ones can still survive.  The role played by databases in MySQL
> is served by schemas in PostgreSQL, so I don't see that there is a
> functional gap here.  I am not sure I'd bother implementing the
> multi-database concept today if we didn't have it already ... but it
> seems kind of pointless to rip it out given that it's already there.

A little trivia: postgres supports full database qualified identifier names:
postgres=# select postgres.public.foo.i from postgres.public.foo;

Even though you can't specify any other database than the one you're in.

merlin


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