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Re: pg_upgrade if 'postgres' database is dropped

From: Thom Brown <thom(at)linux(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_upgrade if 'postgres' database is dropped
Date: 2011-10-28 13:34:02
Message-ID: CAA-aLv6hJxgfAuctJaqSLwrxj1xbin_RkG=Me68_2-QA9jHDLQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 28 October 2011 14:28, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Oct 28, 2011 at 8:12 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> Yes, that would work, but see my summarization email on this.  Using
>> template1 is not a problem for pg_upgrade, it is the modifications to
>> pg_dumpall that are an issue.
>
> I just did a bit of testing on this.  It appears that pg_dumpall, if
> given a cluster containing no postgres database, will happily try to
> connect to template1 instead.  If template1 isn't available either,
> you can use "-l SOMEDBNAME" to specify the name of another database to
> connect to instead.  So there is infinite flexibility there.
>
> But regardless of which database it uses to *generate* the dump, the
> dump itself will *always* contain this, right at the very beginning:
>
> \connect postgres
>
> That line is in fact hard-coded as a literal string in pg_dumpall.c.
> It seems like the easiest fix here might be to just remove that line
> from the dump, because AFAICS it's completely pointless.  During the
> time for which that setting is in effect, we're just restoring
> globals, so it shouldn't matter which database we're connected to;
> only that we have a valid connection.  So trying to switch the
> connection from whatever the user is connected to currently to
> postgres doesn't accomplish anything useful, but it does make it
> possible for dump restoration to unnecessarily fail.

This was the kind of qualm I had with createdb, which I submitted a
patch for earlier this year:
http://archives.postgresql.org/pgsql-hackers/2011-03/msg00999.php

-- 
Thom Brown
Twitter: @darkixion
IRC (freenode): dark_ixion
Registered Linux user: #516935

EnterpriseDB UK: http://www.enterprisedb.com
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