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Re: Versioning policy and pg_upgrade

From: Thom Brown <thom(at)linux(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, jd(at)commandprompt(dot)com, Magnus Hagander <magnus(at)hagander(dot)net>, "w^3" <pgsql-www(at)postgresql(dot)org>
Subject: Re: Versioning policy and pg_upgrade
Date: 2011-01-29 13:34:32
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-www
On 28 January 2011 20:55, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Jan 28, 2011 at 11:52 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>>> "A Major release changes the internal data format of the cluster.
>>> Due to this change a dump/reload of the cluster is required for major
>>> upgrades for upgrading from 8.2 or earlier.
>>> If upgrading from version 8.3 and later, certain installs may be able to
>>> use pg_upgrade (previously named pg_migrator). If pg_upgrade is
>>> compatible with your cluster (see the docs) you will able to perform an
>>> in-place upgrades. Although downtime is still required, this is much
>>> quicker than a dump/restore."
>> Based on this discussion from August, I suggest the following patch be
>> applied to versioning.html.  It mentions pg_upgrade as an major upgrade
>> option and links to the pg_upgrade page that has all the details.
> 1. This is the wrong mailing list for this discussion.
> 2. I think the whole point here is that we've had a policy change: we
> are now making an effort to maintain backward compatibility for data
> files, though not for system tables.  The docs should reflect that.
> Maybe something like:
> Major releases usually change the format of system tables.  These
> changes are often complex, so we do not maintain backward
> compatibility.  Our dump and reload tools do maintain backward
> compatibility and are the most reliable way to perform a major version
> upgrade.  Some major releases also change the internal format of data
> files; however, in recent releases, we have made an attempt to
> minimize such changes.  In cases where the data file formats have not
> changed, pg_upgrade can also be used for major upgrade version
> upgrades; this is typically much faster than a dump and reload.

Only some major releases change the internal format?  I thought it was
best to assume it always did that.

"In cases where the data file formats have not changed"

Don't you mean "have changed"?

"pg_upgrade can also be used for major upgrade version upgrades"

That doesn't read very well.  Perhaps remove the first "upgrade".

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

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