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Re: pg_upgrade if 'postgres' database is dropped

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: 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 13:55:49
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Lists: pgsql-hackers
Robert Haas 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.

If you remove that line, I can modify pg_upgrade to use template1
instead of postgres, and then the user should just remove the postgres
database from the new cluster before the upgrade --- we can give them a
clear error message on that.

  Bruce Momjian  <bruce(at)momjian(dot)us>

  + It's impossible for everything to be true. +

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Subject: Re: pg_upgrade if 'postgres' database is dropped
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