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Re: Upgrading rant.

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Oliver Elphick <olly(at)lfix(dot)co(dot)uk>, Hannu Krosing <hannu(at)tm(dot)ee>,mlw <pgsql(at)mohawksoft(dot)com>, Lamar Owen <lamar(dot)owen(at)wgcr(dot)org>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: Upgrading rant.
Date: 2003-01-05 04:24:14
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Tom Lane wrote:
> Oliver Elphick <olly(at)lfix(dot)co(dot)uk> writes:
> > On Sat, 2003-01-04 at 02:17, Tom Lane wrote:
> >> There isn't any simple way to lock *everyone* out of the DB and still
> >> allow pg_upgrade to connect via the postmaster, and even if there were,
> >> the DBA could too easily forget to do it.
> > I tackled this issue in the Debian upgrade scripts.
> > I close the running postmaster and open a new postmaster using a
> > different port, so that normal connection attempts will fail because
> > there is no postmaster running on the normal port.
> That's a good kluge, but still a kluge: it doesn't completely guarantee
> that no one else connects while pg_upgrade is trying to do its thing.

I was thinking about using GUC:

	#max_connections = 32
	#superuser_reserved_connections = 2

Set both of those to 1, and you lock out everyone but the super-user. 
In fact, we can specify those on postmaster start with -c
max_connections=1, etc.

> I am also concerned about the consequences of automatic background
> activities.  Even the periodic auto-CHECKPOINT done by current code
> is not obviously safe to run behind pg_upgrade's back (it does make
> WAL entries).  And the auto-VACUUM that we are currently thinking of
> is even less obviously safe.  I think that someday, running pg_upgrade
> standalone will become *necessary*, not just a good safety feature.

Yes, certainly we are in major hack mode with pg_upgrade.

  Bruce Momjian                        |
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