Re: Versioning policy and pg_upgrade

On Sat, Jan 29, 2011 at 8:34 AM, Thom Brown <thom@linux.com> wrote:
>> 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"?

No.  The point is, the reason pg_upgrade can work is that the format
of the data files haven't changed.  The catalogs are different, but
all the heaps and indexes are OK (except if you're upgrading from a
version where they're not, in which case life sucks).

> "pg_upgrade can also be used for major upgrade version upgrades"
>
> That doesn't read very well.  Perhaps remove the first "upgrade".

Yeah, typo, sorry.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company