Re: 16-bit page checksums for 9.2

On Thu, Mar 1, 2012 at 4:08 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> So a relation can't have some pages in Version 9.2, and other pages in
>>> version 9.3?  How will this work for 2TB tables?
>
>> Not very well, but better than Tom's proposal to require upgrading the
>> entire cluster in a single off-line operation.
>
> WTF?  That was most certainly not what *I* was proposing; it's obviously
> unworkable.  We need a process that can incrementally up-version a live
> database and keep track of the minimum version present, at some
> granularity smaller than "whole database".
>
> All of this was discussed and hashed out about two years ago, IIRC.
> We just haven't made any progress towards actually implementing those
> concepts.

I am now officially confused. I thought you and Heikki were arguing
about 24 hours ago that we needed to shut down the old database, run a
pre-upgrade utility to convert all the pages, run pg_upgrade, and then
bring the new database on-line; and that, further, you were arguing
that we should not support multiple page versions. Now you seem to be
arguing the exact opposite - namely, that we should support multiple
page versions, and that the conversion should be done on-line.

So, to reiterate, I'm lost.

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